Removed deprecated package Wagtail UI Plus (#199)

Package has become obsolete due to major changes in the Wagtail admin UI. The repository is archived, but still available at: https://github.com/davidconde-nl/wagtailuiplus

README.md

@@ -96,7 +96,6 @@ Awesome Wagtail [![Awesome](https://cdn.rawgit.com/sindresorhus/awesome/d7305f38
 - [wagtail-inventory](https://github.com/cfpb/wagtail-inventory) - Search Wagtail pages by the StreamField blocks they contain.
 - [Wagtail Code Block](https://github.com/FlipperPA/wagtailcodeblock) - StreamField code blocks for the Wagtail CMS with real-time PrismJS Syntax Highlighting.
 - [Wagtail Blocks](https://github.com/ibrahimawadhamid/wagtail_blocks) - A Collection of awesome Wagtail CMS stream-field blocks and Charts.
-- [Wagtail UI Plus](https://github.com/davidcondenl/wagtailuiplus) - Several UI improvements to the Wagtail editor interface for StreamFields and StreamBlocks.
 - [Wagtail Cache Block](https://github.com/AccordBox/wagtail_cache_block) - A templatetag which add HTML fragment cache to your StreamField block
 - [Wagtail UIKit Block](https://github.com/kpsaurus/wagtail-uikitblocks) - A collection of UIKit components that can be used as a Wagtail StreamField block.