CI: remove v14 node tests on PRs

Author: jochem-brouwer

.github/workflows/client-build.yml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [12,14]
+        node-version: [12]
     steps:
       - name: Use Node.js ${{ matrix.node-version }}
         uses: actions/setup-node@v1