Stop testing Python 3.9 against pytest-main.

Support for that version was dropped there.

Author: icemac

tox.ini

@@ -11,7 +11,8 @@ max-line-length = 88
 [tox]
 envlist =
     linting
-    py{39,310,311,312,313,314,py3}-pytest{80,81,82,83,84,main}
+    py{39,310,311,312,313,314,py3}-pytest{80,81,82,83,84}
+    py{310,311,312,313,314,py3}-pytest{main}
     docs
 minversion = 4.0