devel/cmake-core: remove outdated FindOpenMP.cmake patch

This patch broke the build of any armv6/armv7 package that tried to
use OpenMP.  It was once appropriate, but is now no longer correct
or needed.

PR:		270954
MFH:		2023Q2
Approved by:	ports-secteam (fluffy), adridg
Tested by:	portmgr (antoine, exp-run)