ANDROID: uid_sys_stats: remove unnecessary code in procstat switch

No need to aggregate the switched uid separately since
update_io_stats_locked covers all uids.

Bug: 34198239
Change-Id: Ifed347264b910de02e3f3c8dec95d1a2dbde58c0
Signed-off-by: Jin Qian <jinqian@google.com>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>