[RN] Fix dominant speaker and moderator indicators

They are part of the Jitsi font now, there is no need to load them from
FontAwesome.

react/features/filmstrip/components/native/DominantSpeakerIndicator.js

 import React, { Component } from 'react';
 import { View } from 'react-native';
-import Icon from 'react-native-vector-icons/FontAwesome';
+
+import { Icon } from '../../../base/font-icons';
 
 import styles from './styles';
 
         return (
             <View style = { styles.dominantSpeakerIndicatorBackground }>
                 <Icon
-                    name = 'bullhorn'
+                    name = 'dominant-speaker'
                     style = { styles.dominantSpeakerIndicator } />
             </View>
         );

react/features/filmstrip/components/native/ModeratorIndicator.js

 import React, { Component } from 'react';
-import Icon from 'react-native-vector-icons/FontAwesome';
+
+import { Icon } from '../../../base/font-icons';
 
 import styles from './styles';