[CI] Bump Swatinem/rust-cache from 2.0.0 to 2.6.0 (#241)

Bumps [Swatinem/rust-cache](https://github.com/swatinem/rust-cache) from 2.0.0 to 2.6.0.
- [Release notes](https://github.com/swatinem/rust-cache/releases)
- [Changelog](https://github.com/Swatinem/rust-cache/blob/master/CHANGELOG.md)
- [Commits](Swatinem/rust-cache@v2.0.0...v2.6.0)

---
updated-dependencies:
- dependency-name: Swatinem/rust-cache
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/ci.yml

@@ -122,7 +122,7 @@ jobs:
           components: clippy ${{ matrix.toolchain == 'nightly' && ', miri' || '' }}
 
     - name: Rust Cache
-      uses: Swatinem/rust-cache@v2.0.0
+      uses: Swatinem/rust-cache@v2.6.0
       with:
         key: "${{ matrix.target }}"
 
@@ -198,7 +198,7 @@ jobs:
       - uses: actions/checkout@v3
       # Cache the `cargo-readme` installation.
       - name: Rust Cache
-        uses: Swatinem/rust-cache@v2.0.0
+        uses: Swatinem/rust-cache@v2.6.0
       - name: Check README.md
         run: |
           set -e