Add skip-changelog PR label for bump VM PRs (#8627)

This commit adds the `skip-changelog` GitHub label for PRs created by
automation for Bump VM image PRs. Without it, the mandatory
[fragment-in-pr](https://github.com/elastic/elastic-agent/blob/main/.github/workflows/fragment-in-pr.yml)
check is failing thus preventing automerge.

(cherry picked from commit 7a579fa)

# Conflicts:
#	.ci/updatecli/updatecli-bump-vm-images.yml

Author: dliappis

.ci/updatecli/updatecli-bump-vm-images.yml

@@ -24,8 +24,14 @@ actions:
       automerge: false
       labels:
         - dependencies
+<<<<<<< HEAD
         - backport-active-all
       title: '[Automation] Bump VM Image version to {{ source "latestVersion" }}'
+=======
+        - backport-skip
+        - skip-changelog
+      title: '[{{ requiredEnv "BRANCH_NAME" }}][Automation] Bump VM Image version to {{ source "latestVersion" }}'
+>>>>>>> 7a579fab8 (Add skip-changelog PR label for bump VM PRs (#8627))
 
 sources:
   latestVersion: