[Python-buildbots] hg.python.org cert changed, update fingerprint

Infra has updated the cert that serves hg.python.org. If you have hardcoded the fingerprint in your slave's hg config you'll need to update it to:

31:d8:79:0f:ca:b5:c4:76:85:ba:61:84:e7:5b:52:4f:78:7d:38:3e

At least one buildbot seems to be affected by this (PPC64LE Fedora).

--David