GitHub: Delete contributors.yml action and contributors.svg

SVGs are ugly and way too large for our use.

.github/workflows/contributors.yml

@@ -1,17 +0,0 @@
-name: Contributors
-on:
-  schedule:
-    - cron: '0 1 * * 0' # At 01:00 on Sunday.
-  push:
-    branches:
-      - develop
-jobs:
-  contributors:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: wow-actions/contributors-list@v1
-        with:
-          GITHUB_TOKEN: ${{ secrets.SVG_TOKEN }}
-          commitMessage: 'CI: Update contributors.svg'
-          svgPath: 'assets/static/img/contributors.svg'
-          affiliation: 'all'