Fix the grep regex.

Change-Id: I924a310ba44ff17a030cd6f793f135ca9e8758a6
diff --git a/cicd/pipelines/tasks/task_update_unstable.jenkins b/cicd/pipelines/tasks/task_update_unstable.jenkins
index ea8fec0..eb1c43f 100644
--- a/cicd/pipelines/tasks/task_update_unstable.jenkins
+++ b/cicd/pipelines/tasks/task_update_unstable.jenkins
@@ -3,7 +3,7 @@
 String getLatestSnapshot(repository_stem) {
     def script = """
         aptly snapshot list --sort=time --raw \
-            | grep -E '^${repository_stem}-' \
+            | grep -E '^${repository_stem}-[0-9]' \
             | tail -n1
     """