Bump coverage from 4.5.4 to 5.5

Bumps [coverage](https://github.com/nedbat/coveragepy) from 4.5.4 to 5.5.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](nedbat/coveragepy@coverage-4.5.4...coverage-5.5)

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

setup.py

@@ -33,7 +33,7 @@
     install_requires=["aiohttp", "gunicorn", "uvloop", "authlib", "aiocache"],
     extras_require={
         "test": [
-            "coverage==4.5.4",
+            "coverage==5.5",
             "pytest<5.4",
             "pytest-cov",
             "coveralls",