Revert build-ninja condition

Author: ribbanya

.github/workflows/build.yml

@@ -75,7 +75,7 @@ jobs:
   build-ninja:
     name: Ninja
     runs-on: ubuntu-latest
-    if: github.actor == 'doldecomp'
+    if: github.repository == 'doldecomp/melee'
     container: ghcr.io/doldecomp/build-melee:main
     strategy:
       fail-fast: false