Disable tokenizer "Browse" button once tokenizer is full
Summary: Ref T7858. Don't let users add multiple values to single-value tokenizers by using the "Browse" button.
Test Plan:
- Added a token, browse button was disabled.
- Removed the token, browse button was enabled again.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T7858
Differential Revision: https://secure.phabricator.com/D14738