Update pytest-env requirement from ==0.6.* to >=0.6,<0.9

Updates the requirements on [pytest-env](https://github.com/pytest-dev/pytest-env) to permit the latest version.
- [Release notes](https://github.com/pytest-dev/pytest-env/releases)
- [Commits](pytest-dev/pytest-env@0.6.2...0.8.1)

---
updated-dependencies:
- dependency-name: pytest-env
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

setup.py

@@ -39,7 +39,7 @@ def read(*parts):
     'codecov==2.1.*',
     'coverage>=5.3,<6.6',
     'pytest-cov>=2.10,<4.1',
-    'pytest-env==0.6.*',
+    'pytest-env>=0.6,<0.9',
     'pytest>=6.1,<7.2',
     'pycodestyle>=2.6,<2.10'
 ]