chore: update Docker image digest in OwlBot lock file (#8175)

This captures googleapis/synthtool#2174.

Author: codyoss

.github/.OwlBot.lock.yaml

@@ -13,5 +13,5 @@
 # limitations under the License.
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-nodejs-mono-repo:latest
-  digest: sha256:b1ef080074eefaa6ae6c46462034d1f3ceb0b1067e47479d750695ecb3b9fb7e
+  digest: sha256:715766c3cc3c9cee22792364d83af4b7357f36428cddc9b41ae0bc5e95fd59b1
 # created: 2026-03-28T01:31:14.274187079Z