Update coverage requirement from ~=5.5 to ~=6.3 (#1428)

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements_test.txt

@@ -2,7 +2,7 @@
 -r requirements_test_pre_commit.txt
 contributors-txt>=0.7.4
 coveralls~=3.3
-coverage~=5.5
+coverage~=6.3
 pre-commit~=2.19
 pytest-cov~=3.0
 contributors-txt>=0.7.3