LU-15719 doc: Update changelog to properly reflect supported kernels

LU-15719 doc: Update changelog to properly reflect supported kernels

According to https://wiki.lustre.org/Release_2.15.0

Also update e2fsprogs version from the same document

Change-Id: Ife26db67b543bb83651b56df41beaf81fea97721
Signed-off-by: Oleg Drokin <green@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/46993
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Peter Jones <pjones@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>