README.md: clear statement wrt performances

[sylvestre]

No description provided.

[Copilot]

Pull request overview

Updates the project README to better articulate the project’s performance goal and how performance regressions are handled.

Changes:

• Replaces the vague “Improved performances” bullet with a clearer statement about continuous performance improvement and treating significant slowdowns as bugs.

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[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/date/date-locale-hour (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/rm/isatty (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/retry (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/date/resolution (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/misc/sync is no longer failing!
Congrats! The gnu test tests/dd/no-allocate is now passing!

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.