apacheGH-43217: [Java] Remove flight-core shaded jars (apache#43224)

### Rationale for this change

Remove extra jars generated by `flight-core` modules:
- they do not seem to be used by the project internally and does not seem to satisfy some external purpose as well
- they are not compatible with JPMS

### Are these changes tested?

CI/CD

### Are there any user-facing changes?

Several extras jars attached to `org.apache.arrow:flight-core` artifact will stop being published to Apache Maven Repository/Maven Central.
* GitHub Issue: apache#43217

Authored-by: Laurent Goujon <laurent@apache.org>
Signed-off-by: Dane Pitkin <dpitkin@apache.org>

dev/tasks/tasks.yml

@@ -810,10 +810,7 @@ tasks:
       - arrow-vector-{no_rc_snapshot_version}.pom
       - flight-core-{no_rc_snapshot_version}-cyclonedx.json
       - flight-core-{no_rc_snapshot_version}-cyclonedx.xml
-      - flight-core-{no_rc_snapshot_version}-jar-with-dependencies.jar
       - flight-core-{no_rc_snapshot_version}-javadoc.jar
-      - flight-core-{no_rc_snapshot_version}-shaded-ext.jar
-      - flight-core-{no_rc_snapshot_version}-shaded.jar
       - flight-core-{no_rc_snapshot_version}-sources.jar
       - flight-core-{no_rc_snapshot_version}-tests.jar
       - flight-core-{no_rc_snapshot_version}.jar

java/flight/flight-core/pom.xml

@@ -155,71 +155,6 @@ under the License.
           </systemPropertyVariables>
         </configuration>
       </plugin>
-      <plugin>
-        <groupId>org.apache.maven.plugins</groupId>
-        <artifactId>maven-shade-plugin</artifactId>
-        <executions>
-          <execution>
-            <id>shade-main</id>
-            <goals>
-              <goal>shade</goal>
-            </goals>
-            <phase>package</phase>
-            <configuration>
-              <createDependencyReducedPom>false</createDependencyReducedPom>
-              <shadedArtifactAttached>true</shadedArtifactAttached>
-              <shadedClassifierName>shaded</shadedClassifierName>
-              <artifactSet>
-                <includes>
-                  <include>io.grpc:*</include>
-                  <include>com.google.protobuf:*</include>
-                </includes>
-              </artifactSet>
-              <relocations>
-                <relocation>
-                  <pattern>com.google.protobuf</pattern>
-                  <shadedPattern>arrow.flight.com.google.protobuf</shadedPattern>
-                </relocation>
-              </relocations>
-              <transformers>
-                <transformer implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer"></transformer>
-              </transformers>
-            </configuration>
-          </execution>
-          <execution>
-            <id>shade-ext</id>
-            <goals>
-              <goal>shade</goal>
-            </goals>
-            <phase>package</phase>
-            <configuration>
-              <createDependencyReducedPom>false</createDependencyReducedPom>
-              <shadedArtifactAttached>true</shadedArtifactAttached>
-              <shadedClassifierName>shaded-ext</shadedClassifierName>
-              <artifactSet>
-                <includes>
-                  <include>io.grpc:*</include>
-                  <include>com.google.protobuf:*</include>
-                  <include>com.google.guava:*</include>
-                </includes>
-              </artifactSet>
-              <relocations>
-                <relocation>
-                  <pattern>com.google.protobuf</pattern>
-                  <shadedPattern>arrow.flight.com.google.protobuf</shadedPattern>
-                </relocation>
-                <relocation>
-                  <pattern>com.google.common</pattern>
-                  <shadedPattern>arrow.flight.com.google.common</shadedPattern>
-                </relocation>
-              </relocations>
-              <transformers>
-                <transformer implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer"></transformer>
-              </transformers>
-            </configuration>
-          </execution>
-        </executions>
-      </plugin>
       <plugin>
         <groupId>org.xolstice.maven.plugins</groupId>
         <artifactId>protobuf-maven-plugin</artifactId>
@@ -261,23 +196,6 @@ under the License.
           </execution>
         </executions>
       </plugin>
-      <plugin>
-        <artifactId>maven-assembly-plugin</artifactId>
-        <configuration>
-          <descriptorRefs>
-            <descriptorRef>jar-with-dependencies</descriptorRef>
-          </descriptorRefs>
-        </configuration>
-        <executions>
-          <execution>
-            <id>make-assembly</id>
-            <goals>
-              <goal>single</goal>
-            </goals>
-            <phase>package</phase>
-          </execution>
-        </executions>
-      </plugin>
     </plugins>
   </build>