lang/python27,35+: Remove MAKE_JOBS_UNSAFE

ports r393217 via bug 200622 [1] originally set MAKE_JOBS_UNSAFE=yes due to
incorrect uses of recursive make [2], causing intermittent build failures when
run with multiple jobs (-jN).

Upstream committed a fix for the issue in default (3.6, at the time), 3.5 and
2.7 which are now contained in all released lang/python?? port versions. 3.4 did
not receieve a backport merge.

lang/python3.5+ ports inadvertently inherited MAKE_JOBS_UNSAFE=yes, via
repocopies from lang/python34 on their creation, when they were infact safe to
use with -j.

Remove MAKE_JOBS_UNSAFE in all lang/python?? ports except python34 accordingly.

[1] https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=200622
[2] https://bugs.python.org/issue22359

PR:		232308
Reported by:	cem
Reviewed by:	cem
Approved by:	koobs (python)
MFH:		2018Q4
Differential Revision:	D17579

lang/python36/Makefile

@@ -37,7 +37,6 @@ TEST_TARGET=		buildbottest
 TEST_ARGS=		TESTOPTS=-j${MAKE_JOBS_NUMBER}
 
 MAKE_ARGS+=		INSTALL_SHARED="${INSTALL_LIB}"				# Strip shared library
-MAKE_JOBS_UNSAFE=	yes							# Parser/pgen build bug. See Issue: 200622, 201974
 
 SUB_FILES=		pkg-message
 SUB_LIST=		PYTHON_SUFFIX=${PYTHON_SUFFIX}