Reduce PR E2E runner pressure

.github/workflows/tests.yml

@@ -105,13 +105,14 @@ jobs:
     timeout-minutes: 30
     strategy:
       fail-fast: false
-      max-parallel: 4
+      max-parallel: 1
       matrix:
         suite: [core, changed]
         project: [chromium-desktop, chromium-mobile]
     env:
       PLAYWRIGHT_ARTIFACT_NAMESPACE: e2e-pr-${{ matrix.suite }}-${{ matrix.project }}
       PLAYWRIGHT_REPORTER_MODE: line-html
+      PLAYWRIGHT_WORKERS: 1
     steps:
       - name: Repair self-hosted workspace permissions
         shell: bash
@@ -223,6 +224,7 @@ jobs:
             --env CI="${CI:-}" \
             --env PLAYWRIGHT_ARTIFACT_NAMESPACE="$PLAYWRIGHT_ARTIFACT_NAMESPACE" \
             --env PLAYWRIGHT_REPORTER_MODE="$PLAYWRIGHT_REPORTER_MODE" \
+            --env PLAYWRIGHT_WORKERS="$PLAYWRIGHT_WORKERS" \
             --env PLAYWRIGHT_DEV_PORT="$playwright_dev_port" \
             --env MATRIX_SUITE="$MATRIX_SUITE" \
             --env MATRIX_PROJECT="$MATRIX_PROJECT" \