Update dependency @testing-library/react to v12.1.0

Editor assessment

The subject names @testing-library/react and the destination version v12.1.0, which fully determines the change at a glance. The chore type and deps scope are accurate for a test-library maintenance bump, and no body is required because a routine version update carries no motivation beyond dependency upkeep. No footers are present, so there is nothing malformed and nothing noisy to judge. Style hygiene is good: imperative phrasing, no trailing period, no ticket junk, moderate subject length, single language. The message communicates its full content in one unambiguous line, misleads nowhere, and serves as a clean, publishable example of automated maintenance communication.