Update coverage requirement from <6 to <7

Updates the requirements on [coverage](https://github.com/nedbat/coveragepy) to permit the latest version.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](nedbat/coveragepy@coverage-3.0b1...6.5.0)

---
updated-dependencies:
- dependency-name: coverage
  dependency-type: direct:development
...

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

Author: dependabot[bot]

setup.py

@@ -39,7 +39,7 @@ def get_long_description():
     extras_require={
         'docs': ['sphinx>=3.0, <6', 'Pallets-Sphinx-Themes', 'm2r2'],
         'tests': ['pytest'],
-        'tests_cov': ['pytest', 'pytest-cov', 'coverage <6', 'coveralls'],
+        'tests_cov': ['pytest', 'pytest-cov', 'coverage <7', 'coveralls'],
     },
     url='https://github.com/click-contrib/click-option-group',
     project_urls={