Bump coverage from 5.1 to 5.2

Bumps [coverage](https://github.com/nedbat/coveragepy) from 5.1 to 5.2.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](nedbat/coveragepy@coverage-5.1...coverage-5.2)

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

requirements.txt

@@ -7,7 +7,7 @@ better_profanity==0.6.1
 cachecontrol[filecache]==0.12.6
 cachelib==0.1.1
 changelogs==0.14.0
-coverage==5.1
+coverage==5.2
 discord.py[voice]==1.3.3
 feedparser==5.2.1
 flask==1.1.2