#567 fix for ordered factors in tbl_summary

[ddsjoberg]

What changes are proposed in this pull request?
tbl_summary() was erring when summary variables were ordered factors. This PR fixes the bug.

However, the fix does strip the variable label from the ordered factor, and we're not recovering it. I don't think too many people are using ordered factors (this is the first we're hearing of the bug), and of those, how many are using labels? This issue will be addressed in a future pull request #569

If there is an GitHub issue associated with this pull request, please provide link.
closes #567

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Checklist for PR reviewer

• PR branch has pulled the most recent updates from master branch
• NEWS.md has been updated under the heading "# gtsummary (development version)"?
• usethis::use_spell_check() runs with no spelling errors in documentation
• If a new function was added, function included in pkgdown.yml
• If a bug was fixed, a unit test was added for the bug check
• Run pkgdown::build_site(). Check the R console for errors, and review the rendered website.
• Code coverage is suitable for any new functions/features. Review coverage with covr::report().
• R CMD Check runs without errors, warnings, and notes
• When the branch is ready to be merged into master, increment the version number using usethis::use_version(which = "dev"), run codemetar::write_codemeta(), approve, and merge the PR.

[michaelcurry1123]

fixed the bug! @ddsjoberg I will let you merge to master and bump the version since I did not do it right last time!