ci(deps): bump actions/cache from 5 to 6

Bumps [actions/cache](https://github.com/actions/cache) from 5 to 6.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v5...v6)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -45,7 +45,7 @@ jobs:
           toolchain: ${{ matrix.rust }}
 
       - name: Cache cargo registry
-        uses: actions/cache@v5
+        uses: actions/cache@v6
         with:
           path: |
             ~/.cargo/registry
@@ -99,7 +99,7 @@ jobs:
           components: clippy
 
       - name: Cache cargo registry
-        uses: actions/cache@v5
+        uses: actions/cache@v6
         with:
           path: |
             ~/.cargo/registry
@@ -123,7 +123,7 @@ jobs:
           toolchain: nightly-2026-04-16
 
       - name: Cache cargo registry
-        uses: actions/cache@v5
+        uses: actions/cache@v6
         with:
           path: |
             ~/.cargo/registry

.github/workflows/coverage.yml

@@ -39,7 +39,7 @@ jobs:
         run: cargo install cargo-tarpaulin
 
       - name: Cache cargo registry
-        uses: actions/cache@v5
+        uses: actions/cache@v6
         with:
           path: |
             ~/.cargo/registry

.github/workflows/release.yml

@@ -30,7 +30,7 @@ jobs:
         uses: dtolnay/rust-toolchain@stable
 
       - name: Cache cargo registry
-        uses: actions/cache@v5
+        uses: actions/cache@v6
         with:
           path: |
             ~/.cargo/registry
@@ -70,7 +70,7 @@ jobs:
         uses: dtolnay/rust-toolchain@stable
 
       - name: Cache cargo registry
-        uses: actions/cache@v5
+        uses: actions/cache@v6
         with:
           path: |
             ~/.cargo/registry

.github/workflows/security.yml

@@ -49,7 +49,7 @@ jobs:
       - uses: actions/checkout@master
       - name: Install Rust
         run: rustup update stable && rustup default stable
-      - uses: actions/cache@v5
+      - uses: actions/cache@v6
         with:
           path: ${{ runner.tool_cache }}/cargo-vet
           key: cargo-vet-bin-${{ env.CARGO_VET_VERSION }}