tox-envlist is not needed to run tests.
tox version pin is too strict.

--- singledispatch-json-0.5.0/tox.ini.orig
+++ singledispatch-json-0.5.0/tox.ini
@@ -38,8 +38,6 @@
 isolated_build = True
 requires =
     pip>=21,!=22.2
-    tox-envlist>=0.2.1
-    tox~=3.0
     virtualenv!=20.16.0
 
 [envlists]