ci: reduce amount of platforms to run tests on

.github/workflows/pytests.yml

@@ -1,17 +1,18 @@
 name: Unit Tests
 
 on:
-  push:
   pull_request:
+    branches:
+      - master
+  push:
 
 jobs:
   validate:
     strategy:
       fail-fast: false
       matrix:
         python-version: ["3.8", "3.12"]
-        os: ["ubuntu-latest", "windows-latest", "macOS-latest"]
-    runs-on: ${{ matrix.os }}
+    runs-on: "ubuntu-latest"
     steps:
       - uses: actions/checkout@v2
       - name: Set up Python ${{ matrix.python-version }}
@@ -25,7 +26,7 @@ jobs:
           key: pip_cache
       - name: Install depencency
         run: |
-          pip install gql gql[aiohttp] gql[websockets] graphql-core asyncio-atexit pytest
+          pip install gql gql[aiohttp] gql[websockets] graphql-core asyncio-atexit pytest pytest-timeout
       - name: Pytest
         run: |
           python -m pytest tests