test(iostreams): isolate NO_COLOR in detectIsColorEnabled default case

Mikelrequested to merge
mikelolasagasti/glab-cli:fix-test-tmp into main

Description

The "default" subtest assumed no NO_COLOR in the process environment. Fedora's rpmbuild (and other CI) often sets NO_COLOR globally, which made detectIsColorEnabled() correctly return false and broke the test.

Related Issues

Resolves #8272 (closed)

How has this been tested?

Built the package using Fedora's build system with 1.92.1 patched with this MR code.

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