Update lint.yaml

Author: avaneeshk098

.github/workflows/lint.yaml

@@ -1,6 +1,10 @@
 name: Run linter
 
-on: [push, pull_request]
+on:
+  pull_request:
+  push:
+    branches:
+      - master
 
 jobs:
   lint:
@@ -20,4 +24,4 @@ jobs:
         run: |
           python -m pip install pytest black
       - name: Lint
-        run: black .
+        run: black .