chore: delete build size bot (#4334)

We've found a vulnerability in the way we configured this action. See https://securitylab.github.com/research/github-actions-preventing-pwn-requests

.github/workflows/build-size.yml

@@ -1,23 +0,0 @@
-name: Build Size Report
-
-on:
-  pull_request_target:
-    branches:
-      - master
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v2
-        # Workaround for https://github.com/preactjs/compressed-size-action/issues/54
-        with:
-          ref: ${{ github.event.pull_request.head.sha }}
-      - uses: preactjs/compressed-size-action@v2
-        with:
-          repo-token: '${{ secrets.GITHUB_TOKEN }}'
-          build-script: 'build:v2:en'
-          pattern: '{website/build/assets/js/main*js,website/build/assets/css/styles*css,website/build/index.html,website/build/blog/**/introducing-docusaurus/*,website/build/docs/introduction/index.html}'
-          strip-hash: '\.([^;]\w{7})\.'
-          minimum-change-threshold: 30
-          compression: 'none'