Fix Android implementation of setDouble in shared_preferences (flutter#265)

Fixes flutter/flutter#12449

Author: jason-simmons

packages/shared_preferences/android/src/main/java/io/flutter/plugins/sharedpreferences/SharedPreferencesPlugin.java

@@ -115,7 +115,8 @@ public void onMethodCall(MethodCall call, MethodChannel.Result result) {
           result.success(null);
           break;
         case "setDouble":
-          editor.putFloat(key, (float) call.argument("value")).apply();
+          float floatValue = ((Number) call.argument("value")).floatValue();
+          editor.putFloat(key, floatValue).apply();
           result.success(null);
           break;
         case "setInt":