refactor(test): replace os.Setenv with t.Setenv in tests

Description

Replace os.Setenv with t.Setenv in tests.

Related Issues

Resolves #1282 (closed)

How has this been tested?

By running make test

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation
• Chore (Related to CI or Packaging to platforms)
• Test gap
• Refactoring