Rename the GitHub workflow that updates the Git mailing list mirror

Previously, it was on its own, now it's not, so it needs a more
descriptive name.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

.github/workflows/sync.yml renamed to .github/workflows/sync-git-mailing-list-mirror.yml

@@ -1,4 +1,4 @@
-name: sync
+name: sync-git-mailing-list-mirror
 
 on:
   workflow_dispatch:
@@ -13,7 +13,7 @@ env:
 concurrency: sync
 
 jobs:
-  repo-sync:
+  sync-git-mailing-list-mirror:
     runs-on: ubuntu-latest
     permissions:
       contents: write