Align multi-line TextInput onSubmitEditing behavior (#29177)

Summary:
Aligns behavior to be consistent with Android and the [documentation](https://reactnative.dev/docs/textinput#bluronsubmit). `onSubmitEditing` should not be called when `blurOnSubmit=false`.

## Changelog

[iOS] [Fixed] - Align multi-line TextInput onSubmitEditing behavior

Pull Request resolved: #29177

Test Plan: ![textinput-blur-align](https://user-images.githubusercontent.com/4123478/85121116-85b4b200-b224-11ea-86c5-065e9e6d22ba.gif)

Reviewed By: shergin

Differential Revision: D22488870

Pulled By: hramos

fbshipit-source-id: 2dec3a55da6384389a8358896ef1fbfd806d0304

Libraries/Text/TextInput/RCTBaseTextInputView.m

@@ -365,11 +365,13 @@ - (BOOL)textInputShouldReturn
   // `onSubmitEditing` is called when "Submit" button
   // (the blue key on onscreen keyboard) did pressed
   // (no connection to any specific "submitting" process).
-  [_eventDispatcher sendTextEventWithType:RCTTextEventTypeSubmit
-                                 reactTag:self.reactTag
-                                     text:[self.backedTextInputView.attributedText.string copy]
-                                      key:nil
-                               eventCount:_nativeEventCount];
+  if (_blurOnSubmit) {
+    [_eventDispatcher sendTextEventWithType:RCTTextEventTypeSubmit
+                                   reactTag:self.reactTag
+                                       text:[self.backedTextInputView.attributedText.string copy]
+                                        key:nil
+                                 eventCount:_nativeEventCount];
+  }
 
   return _blurOnSubmit;
 }