[26.1 backport] cli-plugins: PluginRunCommand: use cmd.Environ instead of os.Environ

[vvoland]

• backport: https://github.com/docker/cli/pull/5038

• follow-up to https://github.com/docker/cli/pull/5027

Commit 50117590567998307eba377295a1ec24e214ccc7 implemented a fix that caused the current environment to be discarded, using os.Environ(). On Windows, os.Environ() may produce an incorrect value for PWD, for which a new function was added in go1.19;

• https://tip.golang.org/doc/go1.19#osexecpkgosexec
• https://go-review.googlesource.com/c/go/+/401340
• https://github.com/golang/go/issues/50599

Replace the use of os.Environ() with cmd.Environ() to address that.

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[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 61.08%. Comparing base (1e6db5d) to head (1c6a8ec).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## 26.1 #5047 +/- ## ======================================= Coverage 61.08% 61.08% ======================================= Files 295 295 Lines 20664 20663 -1 ======================================= Hits 12623 12623 + Misses 7143 7142 -1 Partials 898 898 ```