fix on-merge testim branch (#483)

Author: cbodonnell

.github/workflows/release-dev.yaml

@@ -145,4 +145,4 @@ jobs:
           license-id: ${{ secrets.STAGING_EMBEDDED_CLUSTER_LICENSE_ID }}
           license: ${{ secrets.STAGING_EMBEDDED_CLUSTER_LICENSE }}
           testim-access-token: ${{ secrets.TESTIM_ACCESS_TOKEN }}
-          testim-branch: ${{ github.head_ref == 'main' && 'master' || github.head_ref }}
+          testim-branch: 'master'