Replace "elevation" in RNTester rows with box-shadow (facebook#46076)

Summary:
Pull Request resolved: facebook#46076

This will add the shadows to iOS as well. let's see if anyone notices 🙂. I also removed dead styles, and removed some of the extra (excessive) padding specific to Android where the previous shadows would overlap.

Changelog: [Internal]

Differential Revision: D61421903

packages/rn-tester/js/components/RNTPressableRow.js

@@ -70,20 +70,16 @@ const styles = StyleSheet.create({
     justifyContent: 'center',
     paddingHorizontal: 15,
     paddingVertical: 12,
-    marginVertical: Platform.select({ios: 4, android: 8}),
-    marginHorizontal: 15,
-    overflow: 'hidden',
-    elevation: 5,
-    backgroundColor: Platform.select({ios: '#FFFFFF', android: '#F3F8FF'}),
+    marginVertical: 4,
+    marginHorizontal: 16,
+    experimental_boxShadow: '0 2px 4px -1px rgba(0, 0, 0, 0.25)',
+    borderRadius: 8,
   },
   descriptionText: {
     fontSize: 12,
     lineHeight: 20,
     marginBottom: 5,
   },
-  pressed: {
-    elevation: 3,
-  },
   topRowStyle: {
     flexDirection: 'row',
     justifyContent: 'space-between',

packages/rn-tester/js/components/RNTesterModuleList.js

@@ -144,15 +144,6 @@ const styles = StyleSheet.create({
     fontWeight: '500',
     fontSize: 11,
   },
-  row: {
-    justifyContent: 'center',
-    paddingHorizontal: 15,
-    paddingVertical: 12,
-    marginVertical: Platform.select({ios: 4, android: 8}),
-    marginHorizontal: 15,
-    overflow: 'hidden',
-    elevation: 5,
-  },
   topRowStyle: {
     flexDirection: 'row',
     justifyContent: 'space-between',