test(unit): exclude darwin from go build constraint

[wangxiaoxuan273]

What this PR does / why we need it:
Removed darwin from go build constraint for pty-related operations. Tested on arm64 Mac and the tests pass.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #1277

Please check the following list:

• Does the affected code have corresponding tests, e.g. unit test, E2E test?
• Does this change require a documentation update?
• Does this introduce breaking changes that would require an announcement or bumping the major version?
• Do all new files have an appropriate license header?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.92%. Comparing base (d2cca28) to head (6cc1437).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1289      +/-   ##
==========================================
- Coverage   81.97%   81.92%   -0.06%     
==========================================
  Files          83       83              
  Lines        3995     3995              
==========================================
- Hits         3275     3273       -2     
- Misses        497      499       +2     
  Partials      223      223              

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[qweeah]

LGTM