fix(controls): Proper foreground on Button content

[dkuaf]

Changes style of Button.xaml to get proper foreground on custom content

Pull request type

Please check the type of change your PR introduces:

• Update
• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes

What is the current behavior?

Wrong foreground on custom content for IsEnabled=false and onpressed

<ui:Button IsEnabled="false">
       <ui:SymbolIcon Symbol="Bug20"/>
</ui:Button>

Issue Number: #1672
fixes #1672

What is the new behavior?

Content Foreground inherhits from parent Foreground

Other information