ci: sync from joshii-h fork instead of upstream

joshii-h/ts6-viewer tracks upstream but lands custom fixes here first,
so syncing from the fork gives us both upstream changes and the fixes
without waiting for upstream merge.

.forgejo/workflows/sync.yaml

@@ -17,7 +17,7 @@ jobs:
 
       - name: Fetch upstream
         run: |
-          git remote add upstream https://github.com/Maxallica/ts6-viewer.git
+          git remote add upstream https://github.com/joshii-h/ts6-viewer.git
           git fetch upstream main
 
       - name: Check for changes