mm/vmscan.c: delete or fix duplicated words

Drop the repeated word "marked".
Change "time time" to "same time".

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Link: http://lkml.kernel.org/r/20200801173822.14973-14-rdunlap@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>