Bump coverage from 6.2 to 6.3

Bumps [coverage](https://github.com/nedbat/coveragepy) from 6.2 to 6.3.
- [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:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

setup.py

@@ -55,7 +55,7 @@
             "Cython==0.29.26",
         ],
         "test": [
-            "coverage==6.2",
+            "coverage==6.3",
             "pytest<6.3",
             "pytest-cov==3.0.0",
             "testfixtures==6.18.3",