fix(e2e): reduce staging E2E concurrency to avoid rate limiting (#8129)

Author: jacekradko

.github/workflows/e2e-staging.yml

@@ -64,6 +64,7 @@ jobs:
 
     strategy:
       fail-fast: false
+      max-parallel: 3
       matrix:
         test-name:
           - 'sessions:staging'