Bump apple-actions/import-codesign-certs from 3 to 6

Bumps [apple-actions/import-codesign-certs](https://github.com/apple-actions/import-codesign-certs) from 3 to 6.
- [Release notes](https://github.com/apple-actions/import-codesign-certs/releases)
- [Commits](Apple-Actions/import-codesign-certs@v3...v6)

---
updated-dependencies:
- dependency-name: apple-actions/import-codesign-certs
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/build_and_test.yml

@@ -125,7 +125,7 @@ jobs:
           ${{ matrix.pluginval-binary }} --strictness-level 10 --verbose --validate "${{ env.VST3_PATH }}"
 
       - name: Import Certificates (macOS)
-        uses: apple-actions/import-codesign-certs@v3
+        uses: apple-actions/import-codesign-certs@v6
         id: keychain
         if: ${{ matrix.name == 'macOS'}}
         with: