test: make cmd/TestInstallInNonGitRepo not affected by actual major.minor versions

[aofei]

This follows up on #1930.

For https://github.com/goplus/gop/actions/runs/9927782432/job/27423172805#step:4:27

=== RUN   TestInstallInNonGitRepo/install_with_VERSION_file
    make_test.go:324: Failed: exit status 2, output: panic: gop/env: [FATAL] Invalid buildVersion: v1.2.98
        
        goroutine 1 [running]:
        github.com/goplus/gop/env.initEnv()
        	/home/runner/work/gop/gop/env/version.go:47 +0x8a
        github.com/goplus/gop/env.init.0()
        	/home/runner/work/gop/gop/env/version.go:38 +0xf

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.29%. Comparing base (9ff7b67) to head (a50c818).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1937   +/-   ##
=======================================
  Coverage   93.29%   93.29%           
=======================================
  Files          42       42           
  Lines       11653    11653           
=======================================
  Hits        10872    10872           
  Misses        624      624           
  Partials      157      157           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.