ci: Only run tket2-py release checks on release PR (#976)

Author: aborgna-q

.github/workflows/release-checks.yml

@@ -1,9 +1,13 @@
-name: Release checks
+# A check that ensures that `tket2-py` works correctly with the latest release of `tket2-exts` and `tket2-eccs`.
+#
+# If this fails, it is likely that the packages require a release before we can release the `tket2` python lib.
+
+name: tket2-py Release checks
 
 on:
   pull_request:
-  merge_group:
-    types: [checks_requested]
+    branches:
+      - release-please--branches--main--components--tket2-py
   workflow_dispatch: {}
 
 env:
@@ -16,42 +20,8 @@ env:
   PYTHON_LOWEST: "3.10"
 
 jobs:
-  # Check if changes were made to the relevant files.
-  # Always returns true if running on the default branch, to ensure all changes are throughly checked.
-  changes:
-    name: Check for changes
-    runs-on: ubuntu-latest
-    # Required permissions
-    permissions:
-      pull-requests: read
-    # Set job outputs to values from filter step
-    # These outputs are always true when running after a merge to main, or if the PR has a `run-ci-checks` label.
-    outputs:
-      rust-release: ${{ steps.source-branch.outputs.rust == 'true' }}
-      python-release: ${{ steps.source-branch.outputs.py == 'true' }}
-    steps:
-    - uses: actions/checkout@v4
-    - name: Override label
-      id: source-branch
-      run: |
-        if [ "${{ github.event_name == 'pull_request' && startsWith(github.head_ref, 'release-please-') }}" == "true" ]; then
-          echo "This is a python release PR"
-          echo "py=true" >> $GITHUB_OUTPUT
-        elif [ "${{ github.event_name == 'pull_request' && startsWith(github.head_ref, 'release-plz-') }}" == "true" ]; then
-          echo "This is a rust release PR"
-          echo "rust=true" >> $GITHUB_OUTPUT
-        elif [ "${{ github.event_name != 'pull_request' }}" == "true" ]; then
-          echo "Manual trigger"
-          echo "py=true" >> $GITHUB_OUTPUT
-          echo "rust=true" >> $GITHUB_OUTPUT
-        else
-          echo "Not a release PR"
-        fi
-
   py-release:
-    name: Check `tket2-py` release
-    needs: changes
-    if: ${{ needs.changes.outputs.python-release == 'true' }}
+    name: Check `tket2-py` release compatibility
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4