[workflows] only run in 'mikf/gallery-dl' repo

The actual code was included in the previous
97a50a23d2 by accident …

This commit only wraps the slightly more complex docker.yml condition
in GitHub's special ${{ … }} braces.

.github/workflows/docker.yml

@@ -22,10 +22,11 @@ jobs:
     runs-on: ubuntu-latest
 
     # on release commits, run only for tag event
-    if: |
+    if: ${{
         github.repository == 'mikf/gallery-dl' &&
         ( ! startsWith( github.event.head_commit.message , 'release version ' ) ||
             startsWith( github.ref , 'refs/tags/v' ) )
+      }}
 
     steps:
     - uses: actions/checkout@v4