#617 Update macOS icons to Big Sur style

Editor assessment

The ticket reference #617 sits between the prefix and the summary, violating description placement: the description should begin immediately after the colon. The remaining summary (update macOS icons to Big Sur style) is clear, and type fix with no scope is acceptable for an asset refresh. No body and no footers. The misplaced issue number is machine-unfriendly clutter exactly where parsers and readers expect prose, which caps this otherwise clean message.