build(forgejo): drop action based on builder

.forgejo/workflows/push-next-on-builder.yml

@@ -1,24 +0,0 @@
-name: Rust
-
-on:
-  push:
-    branches: ["next"]
-  pull_request:
-    branches: ["main"]
-
-env:
-  CARGO_TERM_COLOR: always
-
-jobs:
-  build:
-    runs-on: git-next-builder
-
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-
-      - name: Build
-        run: cargo build --verbose
-
-      - name: Run tests
-        run: cargo test --verbose