selftest: vm: remove deleted local_config.* from .gitignore

Commit d2d6cba5d6623 ("selftest: vm: remove orphaned references to
local_config.{h,mk}") took care of removing orphaned references.  This
commit removes local_config from .gitignore.

Parent patch commit 69007f156ba ("Kselftests: remove support of
libhugetlbfs from kselftests")

Link: https://lkml.kernel.org/r/20220901092315.33619-1-tsahu@linux.ibm.com


Signed-off-by: Tarun Sahu <tsahu@linux.ibm.com>
Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>