Simplify size deltas report job conditional

The previous condition is necessary in repositories where the "Run workflows from fork pull requests" setting is enabled
and the "Send write tokens to workflows from fork pull requests" setting is disabled, explained in more detail here:

https://github.com/arduino/report-size-deltas#run-from-the-same-workflow-as-the-arduinocompile-sketches-action

However, this repository does not have the "Run workflows from fork pull requests" setting enabled, so the extra
condition is superflous and only makes the workflow more difficult to understand and maintain.

Author: per1234

.github/workflows/compile-examples.yml

@@ -108,8 +108,7 @@ jobs:
 
   report-size-deltas:
     needs: compile-test
-    # Only run the job when the workflow is triggered by a pull request from this repository (because arduino/report-size-deltas requires write permissions)
-    if: github.event_name == 'pull_request' && github.event.pull_request.head.repo.full_name == github.repository
+    if: github.event_name == 'pull_request'
     runs-on: ubuntu-latest
     steps:
       - name: Download sketches reports artifact