Fix: replace GitRunners with GitHub's own runners (#1664)

* Fix: replace GitRunners with GitHub's own runners

GitRunners are closing up shop, we need to revert back to the built-in runners offered by GitHub.

* Fix: replace GitRunners with GitHub's own runners

Summary:

GitRunners are closing up shop, we need to revert back to the built-in runners offered by GitHub.

.github/workflows/acceptance_test.yml

@@ -133,8 +133,7 @@ jobs:
     needs: [ fetch-urls, pack-master, pack-snapshot ]
     # We use machines with more memory to run validation, as large feeds
     # can consume too much heap for default machine instances (see #1304).
-    runs-on: gitrunners-ubuntu-2204-x64-4vcpu
-    ## ubuntu-latest-4-cores
+    runs-on: ubuntu-latest-4-cores
     strategy:
       matrix: ${{ fromJson(needs.fetch-urls.outputs.matrix) }}
     steps:

.github/workflows/end_to_end.yml

@@ -63,8 +63,7 @@ jobs:
           name: gtfs-validator-snapshot
           path: cli/build/libs/gtfs-validator-*-cli.jar
   fetch-urls:
-    runs-on: gitrunners-ubuntu-2204-x64-4vcpu
-    ## ubuntu-latest-4-cores
+    runs-on: ubuntu-latest-4-cores
     steps:
       - name: Checkout repository code
         uses: actions/checkout@v3