replace readwrite with assign

@lunaleaps The RCTTextInputComponentView.mm is the iOS Fabric Component for TextInput. Creates an instance _backedTextInput of type [BackedTextInputViewProtocol](https://github.com/facebook/react-native/blob/f0d0186ebad7312cdcd54b74d8d47e47bd4d741b/Libraries/Text/TextInput/RCTBackedTextInputViewProtocol.h#L20) using RCTUITextView or RCTUITextField constructors.
https://github.com/facebook/react-native/blob/f0d0186ebad7312cdcd54b74d8d47e47bd4d741b/React/Fabric/Mounting/ComponentViews/TextInput/RCTTextInputComponentView.mm#L78

BackedTextInputViewProtocol, RCTUITextView and RCTUITextField headers should match (currently they don't, accessibilityErrorMessage type differs in RCTBackedTextInputViewProtocol).
Sorry for the mistake. I'm rebasing, building, testing and pushing the commit soon. Thanks
https://stackoverflow.com/questions/2255861/property-retain-assign-copy-nonatomic-in-objective-c

Author: fabOnReact

Libraries/Text/TextInput/Singleline/RCTUITextField.h

@@ -27,9 +27,9 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nonatomic, strong, nullable) UIColor *placeholderColor;
 @property (nonatomic, assign) UIEdgeInsets textContainerInset;
 @property (nonatomic, assign, getter=isEditable) BOOL editable;
+@property (nonatomic, assign, nullable) NSString *accessibilityErrorMessage;
 @property (nonatomic, readwrite, nullable) NSString *currentAccessibilityError;
 @property (nonatomic, readwrite, nullable) NSString *previousAccessibilityError;
-@property (nonatomic, readwrite, nullable) NSString *accessibilityErrorMessage;
 @property (nonatomic, getter=isScrollEnabled) BOOL scrollEnabled;
 @property (nonatomic, strong, nullable) NSString *inputAccessoryViewID;
 @property (nonatomic, assign, readonly) CGFloat zoomScale;