[Backport 3.5] Remove relative date in IndicesRequestCacheIT - #20953

✅ This commit did not trigger a Mend scan. The conclusion status of this Security Check is 'Successful' because there was no commit in this branch that introduced new vulnerabilities with a score higher than the configured threshold. Review the Mend Security check associated with that commit.
Scan token: aad098ffcaea4518bd0f7816a2a8048f