fix(tox): add lint dependency group for testing unit tests

gentest still requires ruff, cf #1715

Author: danceratopz

tox.ini

@@ -31,6 +31,7 @@ commands =
 # overwrite default groups (dev) to avoid installing optimized in tox envs using pypy
 dependency_groups =
     test
+    lint  # TODO: add ruff for gentest; remove as part of ethereum/execution-specs#1715
 passenv =
     PYPY_GC_MAX
     PYPY_GC_MIN