ci: Update actions/checkout and actions/cache.

This updates these to the current versions which also use more
recent versions of Node, silencing some deprecation warnings from
within GitHub Actions.

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
         channel: [stable, nightly]
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - name: Setup rust toolchain
       uses: dtolnay/rust-toolchain@stable
@@ -27,19 +27,19 @@ jobs:
       run: rustc --version && cargo --version
 
     - name: Cache cargo registry
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       with:
         path: ~/.cargo/registry
         key: ${{ runner.os }}-${{ matrix.channel }}-cargo-registry-${{ hashFiles('**/Cargo.lock') }}
 
     - name: Cache cargo index
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       with:
         path: ~/.cargo/git
         key: ${{ runner.os }}-${{ matrix.channel }}-cargo-index-${{ hashFiles('**/Cargo.lock') }}
 
     - name: Cache cargo build
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       with:
         path: target
         key: ${{ runner.os }}-${{ matrix.channel }}-cargo-build-target-${{ hashFiles('**/Cargo.lock') }}