Disable concurrent integration test runs (#1426)

Integration tests do not work well when running concurrently against
a single AWS account. Also integration tests clean up after themselves
so we don't want them to be canceled in the middle of a run.

.github/workflows/gate.yaml

@@ -21,6 +21,9 @@ jobs:
     runs-on: ubuntu-latest
     permissions:
       id-token: write
+    concurrency:
+      group: ${{ github.workflow }}-${{ github.ref }}
+      cancel-in-progress: false
     steps:
       - uses: actions/checkout@v4
       - name: Install Poetry