Restore this message as stderr because it affects requirements.txt generation

[matteius]

The issue

• pipenv run pip freeze > requirements.txt adds a first line "Loading .env environment variables..." with pipenv version 2022.3.23 #5003
• Allow more control over .env loading message #4027 (comment)

The fix

Restore the logging back to be stderr.

The checklist

• Associated issue
• A news fragment in the news/ directory to describe this fix with the extension .bugfix, .feature, .behavior, .doc. .vendor. or .trivial (this will appear in the release changelog). Use semantic line breaks and name the file after the issue number or the PR #.

[sdepablos]

@matteius does this solve any use case when the output of any pipenv command is redirected to a file. We found ourselves with the same issue when doing pipenv run

[matteius]

@sdepablos Yes, this was only affecting pipenv run my earlier messages said install which was misleading but was what I thought initially this AM. Since we changed it back to stderr it won't be redirected to the file because that only captures stdout. Also, planning to issue a new release tonight to patch up the two known regressions.