NO-JIRA: Update alertmanager restore-upstream list

Signed-off-by: Jayapriya Pai <janantha@redhat.com>

Author: slashpai

.github/workflows/merge-alertmanager.yaml

@@ -24,6 +24,7 @@ jobs:
          CHANGELOG.md
          VERSION
          .promu.yml
+         .gitignore
          go.mod
          go.sum
       assets-cmd: |