sslutil: another use proper attribute to select python 3.7+
The previous attribute was python 3.6+, but guarded a python 3.7+ block
Using the correct attribute avoids:
- File "/tmp/hgtests.bc0_uk2d/install/lib/python/mercurial/sslutil.py", line 577, in wrapserversocket
-
sslcontext.minimum_version = ssl.TLSVersion.TLSv1_1
- AttributeError: module 'ssl' has no attribute 'TLSVersion'