Bump actions/cache from 5 to 6 (#163)

Author: dependabot[bot]

.github/workflows/build-macos.yml

@@ -17,7 +17,7 @@ jobs:
         uses: actions/checkout@v7
 
       - name: Cache Homebrew downloads
-        uses: actions/cache@v5
+        uses: actions/cache@v6
         with:
           path: ~/Library/Caches/Homebrew
           key: brew-qt-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('.github/workflows/macos.yml') }}