git: openjdk/jdk15u-dev: 8274001: Bump update version for OpenJDK: jdk-15.0.6

[Yuri Nesterenko]

Changeset: 21153b99
Author:    Yuri Nesterenko <yan at openjdk.org>
Date:      2021-09-21 14:10:51 +0000
URL:       https://git.openjdk.java.net/jdk15u-dev/commit/21153b99f79318dd9e0acde049b6c1a35c164b47

8274001: Bump update version for OpenJDK: jdk-15.0.6

Reviewed-by: bae

! .jcheck/conf
! make/autoconf/version-numbers