fix: use correct files pattern in karma.config on windows

[Fatme]

PR Checklist

• The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/CONTRIBUTING.md#commit-messages.
• There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
• You have signed the CLA.
• All existing tests are passing: https://github.com/NativeScript/nativescript-cli/blob/master/CONTRIBUTING.md#contribute-to-the-code-base
• Tests for the changes are included.

What is the current behavior?

tns test command does not work on windows on projects with .nsconfig file

What is the new behavior?

tns test command works on windows on projects with .nsconfig file

Fixes/Implements/Closes #[Issue Number].

#4178