Update coverage requirement from <7.6,>=5.3 to >=5.3,<7.7

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-5.3...7.6.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

setup.py

@@ -42,7 +42,7 @@ def read(*parts):
 
 tests_require = [
     'codecov==2.1.*',
-    'coverage>=5.3,<7.6',
+    'coverage>=5.3,<7.7',
     'pytest-cov>=2.10,<5.1',
     'pytest-env==1.1.3',
     'pytest-mock>=3.11,<3.15',