build(tox): align used pkgs, remove py35 and py36

To align test environment with regular deployments, ensure same python packages / requirements
files are used by tox, unsupported python version (py35, py36) removed.

tox.ini

@@ -1,21 +1,16 @@
 [tox]
-envlist = py{35,36,37,38,39}
+envlist = py{37,38,39}
 skipsdist = True
 # If the user is missing an interpreter, don't fail
 skip_missing_interpreters = True
 
-
 [testenv]
-usedevelop = True
 deps =
-    -rrequirements-testing.txt
+    wheel
+    -rrequirements.txt
     -rrequirements-ev.txt
-    python-openid
-    python-openid-teams
-    python-openid-cla
-    pytest-xdist
-    pytest-cov
-    pytest
+    -rrequirements-ci.txt
+    -rrequirements-testing.txt
 install_command =
     pip install {opts} {packages}
 setenv =