Automatically install rust toolchain for CI

.gitea/workflows/ci.yml

@@ -1,14 +1,13 @@
 name: "CI"
 on:
   push:
+  pull_request:
   workflow_dispatch:
 
 jobs:
   formatting:
     name: cargo fmt
     runs-on: ubuntu-latest
-    env:
-      RUNNER_TOOL_CACHE: /toolcache
     steps:
       - uses: actions/checkout@v6
       - uses: actions-rust-lang/setup-rust-toolchain@v1
@@ -20,8 +19,6 @@ jobs:
   test:
     name: cargo test
     runs-on: ubuntu-latest
-    env:
-      RUNNER_TOOL_CACHE: /toolcache
     steps:
       - uses: actions/checkout@v6
       - uses: actions-rust-lang/setup-rust-toolchain@v1
@@ -31,8 +28,6 @@ jobs:
   test-gpu:
     name: cargo test (GPU)
     runs-on: ubuntu-latest
-    env:
-      RUNNER_TOOL_CACHE: /toolcache
     steps:
       - uses: actions/checkout@v6
       - uses: actions-rust-lang/setup-rust-toolchain@v1