Unique tag (#2969)

Author: Abacn

plugins/templates-maven-plugin/src/main/java/com/google/cloud/teleport/plugin/maven/PromoteHelper.java

@@ -228,7 +228,7 @@ String getDigestFromTag(String tag) {
             "images",
             "list-tags",
             targetPath, // This is the image name, e.g., us.gcr.io/my-project/my-image
-            "--filter=tags:" + tag,
+            "--filter=tags=" + tag,
             "--format",
             "get(digest)"
           };