Fix tox4 error

Remove skipsdist that it was never supported and causes breakage
when used with usedevelop.

Change-Id: Ic1cb9d8f0f555e05d35c7e2201187a0b82b48d4c
diff --git a/tox.ini b/tox.ini
index fe7130f..f30cf8a 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,7 +1,6 @@
 [tox]
 minversion = 3.18.0
 envlist = pep8
-skipsdist = True
 ignore_basepython_conflict=true
 
 [testenv]