Update coverage requirement from ~=6.2 to ~=6.3

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@6.2...6.3)

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

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

Author: dependabot[bot]

requirements_test.txt

@@ -1,7 +1,7 @@
 -r requirements_test_pre_commit.txt
 -r requirements_test_min.txt
 coveralls~=3.3
-coverage~=6.2
+coverage~=6.3
 pre-commit~=2.17;python_full_version>="3.6.2"
 tbump~=6.6.0
 pyenchant~=3.2