ws_mempbrk_sse42.c: remove inclusion of stdint.h as it's no more required after g79e4da4

Change-Id: I48776a286ba1d412ecda55857938d9daa77fd3f7
Reviewed-on: https://code.wireshark.org/review/5136
Petri-Dish: Pascal Quantin <pascal.quantin@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Pascal Quantin <pascal.quantin@gmail.com>