Update README.md

Author: jigyasa1411

README.md

@@ -5,7 +5,7 @@ A flutter app demonstrating Shared Preferences for persisting user login details
 
 <table>
   <tr>
-    <td><img src="https://github.com/MarvelApps-Flutter/flutter_shared_preference/blob/dev/screenshots/android/android1.png" height="480px"></td>
+    <td><img src="https://github.com/MarvelApps-Flutter/flutter_shared_preference/blob/master/screenshots/android/android1.png" height="480px"></td>
     <td><img src="https://github.com/MarvelApps-Flutter/flutter_shared_preference/blob/master/screenshots/android/android2.png" height="480px"></td>
     <td><img src="https://github.com/MarvelApps-Flutter/flutter_shared_preference/blob/master/screenshots/android/android3.png" height="480px"></td>
   </tr>