Don't restyle radios and checkboxes in TextBoxWrapper

style.css has this:
```css
.TextBoxWrapper textarea,
.TextBoxWrapper input {
   width: 100%;
   display: block;
}
```
I have a plugin that adds a post format chooser to the activity form and this CSS makes my radio buttons show up weird. I can always re-override, but hey, let's have sensible defaults. This PR makes that block not apply to radios or checkboxes. Tested with 2.1.6.