Update coverage requirement from <4.6,>=4.5 to >=4.5,<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-4.5...7.6.1)

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

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

dev-requirements.txt

@@ -1,6 +1,6 @@
 # Only for testing
 beautifulsoup4>=4.8,<4.9
-coverage>=4.5,<4.6
+coverage>=4.5,<7.7
 pytest
 pytest-cov