chore(ci): Constrain Redshift drivers tests to run 1 test suite at time (#10102)

Author: KSDaemon

.github/workflows/drivers-tests.yml

@@ -241,6 +241,13 @@ jobs:
       # secrets as job-level environment variables, then referencing the environment variables
       # to conditionally run steps in the job.
       DRIVERS_TESTS_ATHENA_CUBEJS_AWS_KEY: ${{ secrets.DRIVERS_TESTS_ATHENA_CUBEJS_AWS_KEY }}
+
+    # redshift Test Serverless Instance is so tiny that it can't serve a few test suites at once,
+    # so we constrain it to 1 test suite at time.
+    concurrency:
+      group: ${{ contains(matrix.database, 'redshift') && 'redshift-global' || format('drivers-tests-{0}-{1}', matrix.database, github.run_id) }}
+      cancel-in-progress: false
+
     strategy:
       matrix:
         database: