CI: Stop testing for node 14

Author: bilelmoussaoui

.github/workflows/flatpak-test.yml

@@ -87,7 +87,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [14.x, 16.x]
+        node-version: [16.x, 18.x, 20.x]
     steps:
       - uses: actions/checkout@v4
       - name: Use Node.js ${{ matrix.node-version }}