test: investigate hanging failover test

Author: karenc-bq

.github/workflows/integration_tests.yml

@@ -57,7 +57,6 @@ jobs:
           RDS_DB_REGION: ${{ secrets.AWS_DEFAULT_REGION }}
           AURORA_MYSQL_DB_ENGINE_VERSION: ${{ matrix.engine-version }}
           AURORA_PG_ENGINE_VERSION: ${{ matrix.engine-version }}
-          NUM_INSTANCES: 2
 
       - name: 'Archive results'
         if: always()