spec: disable neon extension auto upgrade (#7128)

This pull request disables neon extension auto upgrade to help the next
compute image upgrade smooth.

## Summary of changes

We have two places to auto-upgrade neon extension: during compute spec
update, and when the compute node starts. The compute spec update logic
is always there, and the compute node start logic is added in
#7029. In this pull request, we
disable both of them, so that we can still roll back to an older version
of compute before figuring out the best way of extension
upgrade-downgrade. #6936

We will enable auto-upgrade in the next release following this release.

There are no other extension upgrades from release 4917 and therefore
after this pull request, it would be safe to revert to release 4917.

Impact:

* Project created after unpinning the compute image -> if we need to
roll back, **they will stuck**, because the default neon extension
version is 1.3. Need to manually pin the compute image version if such
things happen.
* Projects already stuck on staging due to not downgradeable -> I don't
know their current status, maybe they are already running the latest
compute image?
* Other projects -> can be rolled back to release 4917.

Signed-off-by: Alex Chi Z <chi@neon.tech>

compute_tools/src/spec.rs

@@ -743,19 +743,21 @@ pub fn handle_extension_neon(client: &mut Client) -> Result<()> {
     // which may happen in two cases:
     // - extension was just installed
     // - extension was already installed and is up to date
-    let query = "ALTER EXTENSION neon UPDATE";
-    info!("update neon extension version with query: {}", query);
-    client.simple_query(query)?;
+    // DISABLED due to compute node unpinning epic
+    // let query = "ALTER EXTENSION neon UPDATE";
+    // info!("update neon extension version with query: {}", query);
+    // client.simple_query(query)?;
 
     Ok(())
 }
 
 #[instrument(skip_all)]
-pub fn handle_neon_extension_upgrade(client: &mut Client) -> Result<()> {
-    info!("handle neon extension upgrade");
-    let query = "ALTER EXTENSION neon UPDATE";
-    info!("update neon extension version with query: {}", query);
-    client.simple_query(query)?;
+pub fn handle_neon_extension_upgrade(_client: &mut Client) -> Result<()> {
+    info!("handle neon extension upgrade (not really)");
+    // DISABLED due to compute node unpinning epic
+    // let query = "ALTER EXTENSION neon UPDATE";
+    // info!("update neon extension version with query: {}", query);
+    // client.simple_query(query)?;
 
     Ok(())
 }