Fix typo missing space between "so" and "re-building"

[ptamarit]

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The issue

Given the correct CLI arguments and project, pipenv will show the following message:

Pipfile.lock (abcdef) out of date, but installation uses --system sore-building lockfile must happen in isolation. Please rebuild lockfile in a virtualenv.  Continuing anyway...

The fix

Add the missing space between "so" and "re-building".

The checklist

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

Since this is just a typo, I did not create an issue and I did not create a news, but let me know if you want me to do so.