Revert "fix: Adjust number of max runners to 15"

This reverts commit a33de77.

Author: rikukissa

.github/workflows/deploy-and-e2e.yml

@@ -110,7 +110,7 @@ jobs:
     environment: ${{ github.event.client_payload.stack || github.event.inputs.stack }}
     strategy:
       fail-fast: false
-      max-parallel: 15
+      max-parallel: 10
       matrix:
         test_file: ${{ fromJson(needs.discover-tests.outputs.test_matrix) }}
     name: ${{ matrix.test_file }}