TriStateCheckbox: value doesn't need to be set on the input when chec…

[mrvelker]

TriStateCheckbox: value doesn't need to be set on the input when checked is being used. removed it to prevent the warning "'value' prop on 'input' should not be null" from occurring.

TriStateCheckbox: forced checked to be either true or false to prevent the warning "changing an uncontrolled input to a controlled input". The actual checked value isn't used to determine the state, only to trigger a change.

#7914 #7313