remove unused method and plugin. refs #687

This same function is in `HtmlUtil::getSelector_ModuleTables` and neither the method nor the plugin is used.

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | na
| Fixed tickets | 
| Refs tickets  | 
| License       | MIT
| Doc PR        |