Remove Python3.5 from tox.ini as it is not supported anymore

tox.ini

@@ -2,7 +2,7 @@
 # fakeroot -u tox --recreate
 
 [tox]
-envlist = py{35,36,37,38,39},flake8
+envlist = py{36,37,38,39},flake8
 
 [testenv]
 deps =