Enter the misspelled keyword into the Filter Search box then right-click on the keyword and select 'Delete.' If the count is greater than '0' you need to correct the keyword for those image files before deleting the keyword.
You can also go to Library menu Metadata and select 'Purge Unused Keywords,' which will remove all keywords with 0 tags.
More here: How to use keywords in Lightroom
wobertc you are absolutely correct!
Maybe the option in the Catalog Settings [Clear All Suggestion Lists] will help-
Unfortunately 'Clear All Suggestion Lists' will remove the correctly spelled suggestions. There doesn't appear to be a way to selectively remove misspelled entries, but you can "clear" the suggestions for specific IPTC metadata fields:
This might be helpful if the misspelled suggestions are only in a few fields.