Update actions/cache action to v6

Author: renovate[bot]

.github/workflows/ci-linux.yml

@@ -20,13 +20,13 @@ jobs:
         uses: actions/checkout@v3.5.3
 
       - name: Restore APT cache
-        uses: actions/cache@v3
+        uses: actions/cache@v6
         with:
           path: /var/cache/apt
           key: ${{ runner.os }}-apt
 
       - name: Restore cached SPM dependencies
-        uses: actions/cache@v3
+        uses: actions/cache@v6
         with:
           path: .build
           key: swiftpm-${{ runner.os }}-${{ inputs.swift-version }}-${{ hashFiles('Package.swift') }}

.github/workflows/ci-macos.yml

@@ -18,7 +18,7 @@ jobs:
         uses: actions/checkout@v3.5.3
 
       - name: Restore cached Homebrew dependencies
-        uses: actions/cache@v3.3.1
+        uses: actions/cache@v6.1.0
         with:
           path: |
             ~/Library/Caches/Homebrew/sdl2--*
@@ -27,7 +27,7 @@ jobs:
           restore-keys: ${{ runner.os }}-brew-sdl2-
 
       - name: Restore cached SPM dependencies
-        uses: actions/cache@v3.3.1
+        uses: actions/cache@v6.1.0
         with:
           path: |
             .build/repositories