ci: set E2E max-parallel to 4

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: vdusek

.github/workflows/_tests.yaml

@@ -85,23 +85,23 @@ jobs:
         (github.event_name == 'push' && github.ref == 'refs/heads/master')
       }}
 
-    # E2E tests build and run Actors on the platform. The combination of max-parallel 2 with 16 pytest
+    # E2E tests build and run Actors on the platform. The combination of max-parallel 4 with 16 pytest
     # workers and a global concurrency group is a compromise between stability and performance - it keeps
     # the platform's resource usage in check while still allowing reasonable test throughput.
     concurrency:
       group: e2e-tests
       cancel-in-progress: false
 
     strategy:
-      max-parallel: 2
+      max-parallel: 4
       matrix:
         os: ["ubuntu-latest"]
         python-version: ["3.10", "3.14"]
 
     runs-on: ${{ matrix.os }}
 
     env:
-      TESTS_CONCURRENCY: "8"
+      TESTS_CONCURRENCY: "16"
 
     steps:
       - name: Checkout repository