Typo 'pacrat' -> 'packrat'

[shanecandoit]

Code review checklist

• [x] Pull request represents a single change (i.e. not fixing disparate/unrelated things in a single PR)
• [x] Title summarizes what is changing
• [ ] Commit messages are meaningful (see this for details)
• [ ] Tests have been included and/or updated
• [ ] Docstrings have been included and/or updated, as appropriate
• [ ] Standalone docs have been updated accordingly
• [ ] Changelog(s) has/have been updated, as needed (see CHANGELOG.md, no need to update for typo fixes and such).

[igordejanovic]

Thanks.