fix/mac/Actions: Don't install ninja, already there

Author: TwinFan

.github/actions/build-mac/action.yml

@@ -25,10 +25,6 @@ outputs:
 runs:
   using: "composite"
   steps:
-  - name: Install required libs
-    shell: bash
-    run: |
-      brew install ninja
   - name: Prepare
     shell: bash
     run: |