[CI] Bump Swatinem/rust-cache from 2.7.3 to 2.8.1 (#2819)

Bumps [Swatinem/rust-cache](https://github.com/swatinem/rust-cache) from 2.7.3 to 2.8.1.
- [Release notes](https://github.com/swatinem/rust-cache/releases)
- [Changelog](https://github.com/Swatinem/rust-cache/blob/master/CHANGELOG.md)
- [Commits](Swatinem/rust-cache@23bce25...f13886b)

---
updated-dependencies:
- dependency-name: Swatinem/rust-cache
  dependency-version: 2.8.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -336,7 +336,7 @@ jobs:
           components: clippy, rust-src ${{ matrix.toolchain == 'nightly' && ', miri' || '' }}
 
     - name: Rust Cache
-      uses: Swatinem/rust-cache@23bce251a8cd2ffc3c1075eaa2367cf899916d84 # v2.7.3
+      uses: Swatinem/rust-cache@f13886b937689c021905a6b90929199931d60db1 # v2.8.1
       with:
         key: "${{ matrix.target }}"
 
@@ -689,7 +689,7 @@ jobs:
           echo "RUSTFLAGS=$RUSTFLAGS" >> $GITHUB_ENV
           echo "ZC_TOOLCHAIN=$ZC_TOOLCHAIN" >> $GITHUB_ENV
       - name: Rust Cache
-        uses: Swatinem/rust-cache@23bce251a8cd2ffc3c1075eaa2367cf899916d84 # v2.7.3
+        uses: Swatinem/rust-cache@f13886b937689c021905a6b90929199931d60db1 # v2.8.1
         with:
           key: aarch64_be-unknown-linux-gnu
       - name: Install stable Rust for use in 'cargo.sh'
@@ -721,7 +721,7 @@ jobs:
           echo "RUSTFLAGS=$RUSTFLAGS" >> $GITHUB_ENV
           echo "ZC_TOOLCHAIN=$ZC_TOOLCHAIN" >> $GITHUB_ENV
       - name: Rust Cache
-        uses: Swatinem/rust-cache@23bce251a8cd2ffc3c1075eaa2367cf899916d84 # v2.7.3
+        uses: Swatinem/rust-cache@f13886b937689c021905a6b90929199931d60db1 # v2.8.1
         with:
           key: avr-none
       - name: Install stable Rust for use in 'cargo.sh'