Fixed: Misspelled variable in CPTableView

This commit fixes a typo in CPTableView. `_contentBindingExpicitelySet` should be `_contentBindingExplicitlySet`. The misspelling was consistent, so this should have no functional change.
Merge pull request #1906 from ahankinson/fix-cptableview-variabletypo

Fixed: Misspelled variable in CPTableView