ci: Remove unnecessary macos format check from ci.yml

Author: eureka-cpu

.github/workflows/ci.yml

@@ -29,10 +29,7 @@ jobs:
 
   nix-fmt-check:
     name: Nix Format Check
-    runs-on: ${{ matrix.os }}
-    strategy:
-      matrix:
-        os: [ubuntu-latest, macos-latest]
+    runs-on: ubuntu-latest
 
     steps:
       - uses: actions/checkout@v6