Declaration 'resultPublisher' cannot override more than one superclass declaration

**To Reproduce**

Podfile
```
# Uncomment the next line to define a global platform for your project
# platform :ios, '12.0'

target 'AWSDemo' do
  # Comment the next line if you don't want to use dynamic frameworks
  use_frameworks!

  # Pods for AWSDemo
  pod 'Amplify'
end
```

`pod install` and build

Failed at AmplifyOperation+APIPublishers.swift - line 16
