Console warning for highlightBlock - will be removed entirely in v12.0

Console warning for highlightBlock.

**To recreate:** 
```
import Highlight from 'react-highlight';
...
<Highlight className={language}>
            {some code}
</Highlight>
```

**Appearing message in browser console:**
Deprecated as of 10.7.0. highlightBlock will be removed entirely in v12.0
Deprecated as of 10.7.0. Please use highlightElement now.