Return 304 only when the file is unchanged since If-Modified-Since - #23

The strategy configuration was canceled because "tests.ubuntu-latest_8_1" failed

This request has been automatically failed because it uses a deprecated version of `actions/cache: v2`. Please update your workflow to use v3/v4 of actions/cache to avoid interruptions. Learn more: https://github.blog/changelog/2024-12-05-notice-of-upcoming-releases-and-breaking-changes-for-github-actions/#actions-cache-v1-v2-and-actions-toolkit-cache-package-closing-down