Fix sync_main_to_latest workflow (#206)

* Fix sync_to_main workflow to fetch branches before merging main to
latest.

Git fetch.

Merge origin main

* Remove test branch.

.github/workflows/sync_main_latest.yml

@@ -1,5 +1,6 @@
 name: Sync main and latest
 on:
+  workflow_dispatch:
   push:
     branches:
       - main
@@ -13,7 +14,7 @@ jobs:
         uses: actions/checkout@v3
 
       - name: Merge main into latest
-        run: git checkout latest && git merge main
+        run: git fetch && git switch latest && git merge origin/main
 
       - name: Create pull request
         id: cpr