package/redis: security bump to v6.2.4

package/redis: security bump to v6.2.4

From the release notes:
================================================================================
Redis 6.2.4 Released Tue July 1 12:00:00 IST 2021
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Upgrade urgency: SECURITY, Contains fixes to security issues that affect
authenticated client connections. MODERATE otherwise.
Fix integer overflow in STRALGO LCS (CVE-2021-32625)

Read the whole release note on:
https://github.com/redis/redis/blob/6.2.4/00-RELEASENOTES

Signed-off-by: Titouan Christophe <titouanchristophe@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>