Try to update the E2E parallelization

Author: vdusek

.github/workflows/_tests.yaml

@@ -86,15 +86,19 @@ jobs:
       }}
 
     strategy:
-      max-parallel: 1  # E2E tests build and run Actors on the platform, limit parallelism to avoid exceeding memory limits.
+      # E2E tests build and run Actors on the platform. Limit parallel workflows to 2 to allow running both
+      # the oldest and newest Python versions simultaneously, while not exceeding the platform's limits. Two
+      # parallel workflows with 8 pytest workers each is a compromise between good test parallelization and
+      # not being rate-limited by the platform.
+      max-parallel: 2
       matrix:
         os: ["ubuntu-latest"]
         python-version: ["3.10", "3.14"]
 
     runs-on: ${{ matrix.os }}
 
     env:
-      TESTS_CONCURRENCY: "16"
+      TESTS_CONCURRENCY: "8"
 
     steps:
       - name: Checkout repository