Update feature-removal-update.txt with 3.x versioning

Update all future kernel version entries in feature-removal-schedule.txt
with appropriate 3.x kernel numbering.

Signed-off-by: Deepak Saxena <dsaxena@plexity.net>
Reviewed-by: Jesper Juhl <jj@chaosbits.net>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>