Update the upper bound for coverage

Local test run was generating tons of

> django-click/.tox/dj50/lib/python3.14/site-packages/coverage/parser.py:374: DeprecationWarning: co_lnotab is deprecated, use co_lines instead.

warning

Author: ulgens

requirements-test.txt

@@ -1,7 +1,7 @@
 -r requirements.txt
 
 pytest
-coverage<5
+coverage<8
 pytest-django
 pytest-cov
 pytest-flake8