Remove pull request action (#59)

.github/workflows/pull_request.yml

@@ -1,18 +0,0 @@
-name: Build website
-on: pull_request
-jobs:
-  build:
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v1
-
-      - name: Install Node v12
-        uses: actions/setup-node@v1
-        with:
-          node-version: 12
-
-      - name: Build website
-        run: |
-          npm install
-          npm run build