hg: always import hgdemandimport

The deleted if condition is always true now that we dropped Python 2
and 3.5.

Differential Revision: https://phab.mercurial-scm.org/D12361

hg

@@ -43,7 +43,6 b' from hgdemandimport import tracing'
 with tracing.log('hg script'):
     # enable importing on demand to reduce startup time
     try:
-        if sys.version_info[0] < 3 or sys.version_info >= (3, 6):
             import hgdemandimport
 
             hgdemandimport.enable()