Coverage does not skip tests folder

[PokhodenkoSA]

omit = dpctl/tests/*, dpctl/_version.py does not skip coverage for tests folder.
https://teamcity-or.intel.com/buildConfiguration/Sat_NewCi_IndividualPackages_Dpctl_Development_Python37_Linux_TestingConda/7993260?buildTab=log&focusLine=11148&linesState=11148

Originally posted by @PokhodenkoSA in #369 (comment)