Change staging branch in .gitlab-ci.yml to staging-30c

Co-authored-by: Jenkins staging reset job <[email protected]>

Author: dd-octo-sts[bot]

.gitlab-ci.yml

@@ -1,5 +1,5 @@
 variables:
-  CURRENT_STAGING: staging-30b
+  CURRENT_STAGING: staging-30c
   DOCKER_IMAGE: "registry.ddbuild.io/docker:24.0.4-gbi-focal"
   CI_IMAGE_REPO: "registry.ddbuild.io/ci/commit-headless"
   # Built on main commit 887ca009df25f0f20054dcb9cde962a8fc918ce6