Dropped support for pytest 6

According to the [ClickPy data for pytest](https://clickpy.clickhouse.com/dashboard/pytest?min_date=2025-01-01&max_date=2025-10-07),
pytest v6 represents a very small fraction of downloads, so I think it's
fine to remove support for it.

Author: edgarrmondragon

pyproject.toml

@@ -40,7 +40,7 @@ classifiers = [
 ]
 keywords = ["ansible", "testing", "molecule", "plugin"]
 dependencies = [
-    "pytest>=6.0.0"
+    "pytest>=7.0.0"
 ]
 
 [project.urls]

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 envlist =
-    py{38,39,310,311,312,313}-pytest{6,7,8}
+    py{38,39,310,311,312,313}-pytest{7,8}
 
 [gh-actions]
 python =
@@ -13,15 +13,13 @@ python =
 
 [gh-actions:env]
 PYTEST_MAJOR_VERSION =
-    6: pytest6
     7: pytest7
     8: pytest8
 
 [testenv]
 min_version = 4.22.0
 groups = test
 deps =
-    pytest6: pytest>=6.0.0,<7.0.0
     pytest7: pytest>=7.0.0,<8.0.0
     pytest8: pytest>=8.0.0,<9.0.0