mingw: drop MakeMaker reference

In 20d2a30 (Makefile: replace perl/Makefile.PL with simple make
rules, 2017-12-10), Git stopped using MakeMaker. Therefore, that
definition in the MINGW-specific section became useless.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

config.mak.uname

@@ -530,7 +530,6 @@ ifneq (,$(findstring MINGW,$(uname_S)))
 	NO_STRTOUMAX = YesPlease
 	NO_MKDTEMP = YesPlease
 	NO_SVN_TESTS = YesPlease
-	NO_PERL_MAKEMAKER = YesPlease
 	RUNTIME_PREFIX = YesPlease
 	HAVE_WPGMPTR = YesWeDo
 	NO_ST_BLOCKS_IN_STRUCT_STAT = YesPlease