[CM-715] Mark overridable extension methods as @objc

[mpospese]

Introduction

Compiling our framework in Xcode 14 revealed two new compiler warnings.

/Users/mpospese/Source/YML/Aether/Y-Core-UI/Sources/YCoreUI/Extensions/UIKit/UIScrollView+keyboardNotifications.swift:53:5: warning build: Non-'@objc' instance method in extensions cannot be overridden; use 'public' instead

/Users/mpospese/Source/YML/Aether/Y-Core-UI/Sources/YCoreUI/Extensions/UIKit/UIScrollView+keyboardNotifications.swift:72:5: warning build: Non-'@objc' instance method in extensions cannot be overridden; use 'public' instead

Purpose

Fix the problem that was triggering the compiler warning.

Scope

Minor change to UIScrollView extension for keyboard avoidance

Discussion

The compiler recommendation was to change open to public but because these two methods are intended to be overridden, I added @objc decorator instead (which allows them to be correctly overridden).