Remove deprecated @protobuf ts/plugin framework (#721)

Author: timostamm

.github/workflows/ci.yaml

@@ -60,17 +60,3 @@ jobs:
       - run: npm ci
       - run: npx turbo run conformance
       - run: node scripts/gh-diffcheck.js
-
-  bootstrap:
-    runs-on: ubuntu-24.04
-    steps:
-      - uses: actions/checkout@v4
-      - uses: actions/cache@v4
-        with:
-          path: .turbo
-          key: protobuf-ts-ci/bootstrap/${{ github.sha }}
-          restore-keys: protobuf-ts-ci/bootstrap
-      - run: npm ci
-      - run: npx turbo run @protobuf-ts/plugin#build
-      - run: npx turbo run bootstrap
-      - run: node scripts/gh-diffcheck.js