ci: fail psalm when baseline update required

Signed-off-by: Daniel Kesselberg <mail@danielkesselberg.de>

.github/workflows/static-code-analysis.yml

@@ -36,7 +36,7 @@ jobs:
 
       - name: Show potential changes in Psalm baseline
         if: always()
-        run: git diff -- . ':!lib/composer'
+        run: git diff --exit-code -- . ':!lib/composer'
 
       - name: Upload Analysis results to GitHub
         if: always()
@@ -98,4 +98,4 @@ jobs:
 
       - name: Show potential changes in Psalm baseline
         if: always()
-        run: git diff -- . ':!lib/composer'
+        run: git diff --exit-code -- . ':!lib/composer'