Bug 1616584 - Run `mach mozregression` with Python 3 r=ahal

Differential Revision: https://phabricator.services.mozilla.com/D67555

--HG--
extra : moz-landing-system : lando

mach

@@ -49,7 +49,6 @@ py2commands="
     mochitest
     mozbuild-reference
     mozharness
-    mozregression
     package
     package-multi-locale
     pastebin