ci: revert verify-runner-url extractor to grep src/aws.js

Paired with the full Phase 4 revert — now that action.yml no longer
has a runner-version default, the Phase 4 version of verify-runner-url
that reads action.yml can't find the version. Restore the original
extractor that greps the literal URL out of src/aws.js.

Signed-off-by: yuriyryabikov <22548029+kurok@users.noreply.github.com>

Author: kurok

.github/workflows/pr.yml

@@ -68,20 +68,16 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v4
-      - name: Extract default runner version from action.yml
+      - name: Extract runner version from src/aws.js
         id: extract
         run: |
-          # action.yml declares:
-          #   runner-version:
-          #     ...
-          #     default: '2.333.1'
-          version=$(awk '/^  runner-version:/{found=1} found && /^    default:/{gsub(/[^0-9.]/, "", $2); print $2; exit}' action.yml)
+          version=$(grep -oE 'actions/runner/releases/download/v[0-9]+\.[0-9]+\.[0-9]+' src/aws.js | head -1 | sed 's|.*/v||')
           if [ -z "$version" ]; then
-            echo "::error::Could not locate the default runner-version in action.yml"
+            echo "::error::Could not locate the pinned actions/runner version in src/aws.js"
             exit 1
           fi
           echo "version=$version" >> "$GITHUB_OUTPUT"
-          echo "Default actions/runner: v$version"
+          echo "Pinned actions/runner: v$version"
       - name: HEAD check the Linux x64 release asset
         env:
           VERSION: ${{ steps.extract.outputs.version }}