bitbake.conf, sanity.bbclass: Drop mercurial-native

We have no hg URIs in the metadata, so don't require and don't
ASSUME_PROVIDED it either.  meta-oe has a mercurial-native recipe
if hg URIs are added in a recipe later.

(From OE-Core rev: 6473c9096bf4995c21147e737322d800219c89ab)

Signed-off-by: Tom Rini <tom_rini@mentor.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/conf/bitbake.conf

@@ -132,7 +132,6 @@ ASSUME_PROVIDED = "\
     cvs-native \
     grep-native \
     diffstat-native \
-    mercurial-native \
     patch-native \
     perl-native-runtime \
     python-native-runtime \