Revert "build: AR exit gate YAML to declare dependencies.gitSource (#3929)"

This reverts commit 4c5a1c4.

Author: meltsufin

internal/librariangen/cloudbuild-exitgate.yaml

@@ -42,11 +42,4 @@ options:
     requestedVerifyOption: VERIFIED  # For provenance attestation generation
     logging: CLOUD_LOGGING_ONLY
 images:
-  - us-central1-docker.pkg.dev/cloud-sdk-librarian-prod/images-dev/librarian-java:latest
-dependencies:
-- gitSource:
-    repository:
-      url: "${_LOUHI_REPOSITORY_URL}"
-    revision: "${_LOUHI_REF_SHA}"
-    destPath: "."
-
+  - us-central1-docker.pkg.dev/cloud-sdk-librarian-prod/images-dev/librarian-java:latest