hghave: remove unused check for bdist_mpkg stable

hghave: remove unused check for bdist_mpkg

--- a/tests/hghave.py	Wed Apr 27 10:20:36 2016 -0500
+++ b/tests/hghave.py	Fri Apr 29 14:14:00 2016 -0500
@@ -456,14 +456,6 @@
 def has_osx():
     return sys.platform == 'darwin'
 
-@check("bdistmpkg", "bdist_mpkg Python Package")
-def has_bdistmpkg():
-    try:
-        import bdist_mpkg.script_bdist_mpkg
-        return True
-    except ImportError:
-        return False
-
 @check("osxpackaging", "OS X packaging tools")
 def has_osxpackaging():
     try: