MAINT: Bump pytest-cov from 2.7.1 to 2.8.1
MAINT: Bump pytest-cov from 2.7.1 to 2.8.1

Bumps [pytest-cov](https://github.com/pytest-dev/pytest-cov) from 2.7.1 to 2.8.1.
- [Release notes](https://github.com/pytest-dev/pytest-cov/releases)
- [Changelog](https://github.com/pytest-dev/pytest-cov/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/pytest-dev/pytest-cov/compare/v2.7.1...v2.8.1)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
jorisvandenbossche/numpy,jakirkham/numpy,madphysicist/numpy,abalkin/numpy,jorisvandenbossche/numpy,simongibbons/numpy,charris/numpy,rgommers/numpy,grlee77/numpy,mhvk/numpy,rgommers/numpy,jakirkham/numpy,grlee77/numpy,numpy/numpy,grlee77/numpy,grlee77/numpy,pdebuyl/numpy,mattip/numpy,WarrenWeckesser/numpy,charris/numpy,mhvk/numpy,WarrenWeckesser/numpy,pbrod/numpy,mattip/numpy,WarrenWeckesser/numpy,charris/numpy,mattip/numpy,anntzer/numpy,mattip/numpy,pdebuyl/numpy,numpy/numpy,pbrod/numpy,pdebuyl/numpy,jakirkham/numpy,simongibbons/numpy,jakirkham/numpy,madphysicist/numpy,rgommers/numpy,jorisvandenbossche/numpy,pbrod/numpy,mhvk/numpy,charris/numpy,pbrod/numpy,simongibbons/numpy,abalkin/numpy,WarrenWeckesser/numpy,seberg/numpy,madphysicist/numpy,anntzer/numpy,numpy/numpy,seberg/numpy,jorisvandenbossche/numpy,pdebuyl/numpy,anntzer/numpy,endolith/numpy,simongibbons/numpy,endolith/numpy,madphysicist/numpy,seberg/numpy,jorisvandenbossche/numpy,WarrenWeckesser/numpy,pbrod/numpy,rgommers/numpy,anntzer/numpy,jakirkham/numpy,simongibbons/numpy,grlee77/numpy,numpy/numpy,mhvk/numpy,endolith/numpy,endolith/numpy,madphysicist/numpy,seberg/numpy,abalkin/numpy,mhvk/numpy