requirements: update pytest-cov requirement from <=2.10.1 to <2.11.1

Updates the requirements on [pytest-cov](https://github.com/pytest-dev/pytest-cov) to permit the latest version.
- [Release notes](https://github.com/pytest-dev/pytest-cov/releases)
- [Changelog](https://github.com/pytest-dev/pytest-cov/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest-cov@v1.0...v2.11.0)

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

dev_requirements.txt

@@ -1,7 +1,7 @@
 jupyter<=1.0.0
 pytest<6.2.2
 pytest-benchmark<=3.2.3
-pytest-cov<=2.10.1
+pytest-cov<2.11.1
 pytest-helpers-namespace<=2019.1.8
 pytest-profiling<=1.7.0
 pytest-pycodestyle<=2.2.0