fork-comment-fix: remove ambiguous question mark in CLONE_CHILD_CLEARTID comment

fork-comment-fix: remove ambiguous question mark in CLONE_CHILD_CLEARTID comment

The current comment "Clear TID on mm_release()?" ends with a question
mark, implying uncertainty about whether the TID is actually cleared in
mm_release().

However, the code flow is deterministic.  When a task exits, mm_release()
explicitly checks 'tsk->clear_child_tid' and clears.

Since this behavior is unambiguous, remove the confusing question mark and
rephrase the comment to clearly state that TID is cleared in mm_release().

Link: https://lkml.kernel.org/r/20251125000407.24470-1-s9430939@naver.com
Signed-off-by: Minu Jin <s9430939@naver.com>
Cc: Ben Segall <bsegall@google.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mel Gorman <mgorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>