⬆️ deps: Update actions/cache action to v6 (#72)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/copilot-setup-steps.yml

@@ -23,7 +23,7 @@ jobs:
           toolchain: stable
           components: clippy, rustfmt
 
-      - uses: actions/cache@v5
+      - uses: actions/cache@v6
         id: cargo-cache
         with:
           path: |

.github/workflows/lint-and-fmt.yml

@@ -22,7 +22,7 @@ jobs:
         with:
           toolchain: stable
           components: clippy, rustfmt
-      - uses: actions/cache@v5
+      - uses: actions/cache@v6
         id: cargo-cache
         with:
           path: |

.github/workflows/test.yml

@@ -18,7 +18,7 @@ jobs:
         uses: actions/checkout@v7
       - name: Update rust toolchain
         run: rustup update
-      - uses: actions/cache@v5
+      - uses: actions/cache@v6
         id: cargo-cache
         with:
           path: |