[fenix] Close https://github.com/mozilla-mobile/fenix/issues/28137: Disable run-build tasks on Pull Requests

.github/workflows/build-contributor-pr.yml

@@ -3,7 +3,7 @@ on: [pull_request]
 jobs:
   run-build:
     runs-on: ubuntu-20.04
-    if: github.event.pull_request.head.repo.full_name != github.repository && github.actor != 'MickeyMoz'
+    if: ${{ false }}
     steps:
       - name: Checkout repository
         uses: actions/checkout@v2
@@ -108,7 +108,6 @@ jobs:
   run-ui:
     runs-on: macos-11
     if: ${{ false }}
-
     timeout-minutes: 60
     strategy:
       matrix: