fix(css): default background for server version

Text files are rendered as code blocks.
Do not apply the prosemirror style to keep the background color.

Signed-off-by: Max <max@nextcloud.com>

src/components/Reader.vue

@@ -50,7 +50,6 @@ export default {
 <style lang="scss">
 
 	#read-only-editor {
-		@import './../../css/prosemirror';
 		overflow: scroll;
 	}