ci: bump actions/checkout v4→v6, actions/cache v4→v5 (Node 20 deprecation)

Author: grove

.github/workflows/ci.yml

@@ -16,15 +16,15 @@ jobs:
     name: Check, fmt, clippy, test
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install stable toolchain
         uses: dtolnay/rust-toolchain@stable
         with:
           components: rustfmt, clippy
 
       - name: Cache cargo registry
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         with:
           path: |
             ~/.cargo/registry
@@ -49,7 +49,7 @@ jobs:
     name: Build no_std (alloc only)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install stable toolchain
         uses: dtolnay/rust-toolchain@stable
@@ -67,7 +67,7 @@ jobs:
     name: Minimum supported Rust version
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install Rust 1.85 (MSRV)
         uses: dtolnay/rust-toolchain@1.85.0
@@ -79,7 +79,7 @@ jobs:
     name: Semver compatibility
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Check semver
         uses: obi1kenobi/cargo-semver-checks-action@v2
@@ -92,7 +92,7 @@ jobs:
     runs-on: ubuntu-latest
     if: startsWith(github.ref, 'refs/tags/v')
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install stable toolchain
         uses: dtolnay/rust-toolchain@stable