fix: cypress tests checkout workspace branch (#252)

Signed-off-by: Lin Wang <wonglam@amazon.com>
(cherry picked from commit 734c890)
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

.github/workflows/cypress_workflow.yml

@@ -30,7 +30,7 @@ on:
 
 env:
   TEST_REPO: ${{ inputs.test_repo != '' && inputs.test_repo || 'opensearch-project/opensearch-dashboards-functional-test' }}
-  TEST_BRANCH: "${{ inputs.test_branch != '' && inputs.test_branch || github.base_ref }}"
+  TEST_BRANCH: "${{ inputs.test_branch != '' && inputs.test_branch || 'workspace' }}"
   FTR_PATH: 'ftr'
   START_CMD: 'node ../scripts/opensearch_dashboards --dev --no-base-path --no-watch --savedObjects.maxImportPayloadBytes=10485760 --server.maxPayloadBytes=1759977 --logging.json=false --data.search.aggs.shardDelay.enabled=true'
   OPENSEARCH_SNAPSHOT_CMD: 'node ../scripts/opensearch snapshot -E cluster.routing.allocation.disk.threshold_enabled=false'