Run CI only on main

.github/workflows/ci.yml

@@ -1,38 +1,35 @@
 name: Continuous Integration
-on: [push, pull_request]
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
 jobs:
   lint:
-    # We want to run on external PRs, but not on our own internal PRs as they'll be run
-    # by the push to the branch. Without this if check, checks are duplicated since
-    # internal PRs match both the push and pull_request events.
-    if: github.event_name == 'push' || github.event.pull_request.head.repo.full_name
-      != github.repository
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
         uses: actions/checkout@v3
       - name: Set up Python
         uses: actions/setup-python@v4
         with:
-          python-version: '3.10'
+          python-version: "3.10"
       - name: Run pre-commit
         uses: pre-commit/[email protected]
   test:
-    if: github.event_name == 'push' || github.event.pull_request.head.repo.full_name
-      != github.repository
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
         uses: actions/checkout@v3
       - name: Set up Python
         uses: actions/setup-python@v4
         with:
-          python-version: '3.10'
+          python-version: "3.10"
       - name: Set up Java
         uses: actions/setup-java@v3
         with:
           distribution: adopt
-          java-version: '17'
+          java-version: "17"
       - name: Install poetry
         uses: snok/install-poetry@v1
       - name: Install dependencies