Fixed transparent border around UIExplorer headers

Summary:
public

This was caused by the change to background color propagation, but was actually due to having an unnecessary wrapper view around the headers, which was itself a workaround for a padding bug that was fixed some time ago :-)

Reviewed By: tadeuzagallo

Differential Revision: D2830890

fb-gh-sync-id: b64e701dedb90b357ed7c463b745de021f38637b

Examples/UIExplorer/UIExplorerListBase.js

@@ -87,11 +87,9 @@ class UIExplorerListBase extends React.Component {
 
   _renderSectionHeader(data: any, section: string) {
     return (
-      <View style={styles.sectionHeader}>
-        <Text style={styles.sectionHeaderTitle}>
-          {section.toUpperCase()}
-        </Text>
-      </View>
+      <Text style={styles.sectionHeader}>
+        {section.toUpperCase()}
+      </Text>
     );
   }
 
@@ -148,14 +146,12 @@ var styles = StyleSheet.create({
   },
   sectionHeader: {
     padding: 5,
+    fontWeight: '500',
+    fontSize: 11,
   },
   group: {
     backgroundColor: 'white',
   },
-  sectionHeaderTitle: {
-    fontWeight: '500',
-    fontSize: 11,
-  },
   row: {
     backgroundColor: 'white',
     justifyContent: 'center',