Move all PR tests to free tier (#25930)

After moving only contributor PRs to free tier it was
observed that the tests actually finish faster in free tier
than with larger runners. We have let the change soak for about
a month now without any issues.

Therefore we move to free tier runners for all PRs.
```release-note
NONE
```

Co-authored-by: Mattermost Build <build@mattermost.com>

.github/workflows/server-test-template.yml

@@ -16,24 +16,9 @@ on:
         type: string
 
 jobs:
-  choose-runner:
-    runs-on: ubuntu-latest
-    outputs:
-      runner: ${{ steps.determine-runner.outputs.runner }}
-    steps:
-      - name: test/check-if-contributor-pr
-        id: determine-runner
-        run: |
-          if ${{ github.event.pull_request.head.repo.full_name == github.event.pull_request.base.repo.full_name }}
-            then
-              echo "runner=ubuntu-latest-8-cores" >> "$GITHUB_OUTPUT"
-            else
-              echo "runner=ubuntu-22.04" >> "$GITHUB_OUTPUT"
-          fi
   test:
-    needs: choose-runner
     name: ${{ inputs.name }}
-    runs-on: ${{ needs.choose-runner.outputs.runner }}
+    runs-on: ubuntu-22.04
     env:
       COMPOSE_PROJECT_NAME: ghactions
     steps: