Typo for square feet area of multi-family

[joseph-robertson]

Pull Request Description

Closes #1114.

CI results show that this affects only a handful of testing project datapoints, and no national project datapoints.

Checklist

Not all may apply:

• [ ] Tests (and test files) have been updated
• [ ] Documentation has been updated
  • [ ] If related to resstock-estimation, checklist includes data dictionary, source report, options_lookup
• [ ] Changelog has been updated
• [ ] openstudio tasks.rb update_measures has been run
• [ ] No unexpected regression test changes on CI (checked comparison artifacts)