Gutenberg/Publicize: Don't enqueue social logos anymore (#11096)

Don't enqueue social logos anymore, since they're now taken care of on the client side (per Automattic/wp-calypso#29317)


#### Changes proposed in this Pull Request:

Remove `wp_enqueue_style( 'social-logos' );` from `class.jetpack-gutenberg.php`.

#### Testing instructions:

- Start writing a new post
- Click 'Publish'
- Make sure you have a couple of Publicize connections 
- Verify that the social logos next to each connections are still there

![image](https://user-images.githubusercontent.com/96308/50794495-917c1500-12cb-11e9-85be-e61fa217e168.png)

#### Proposed changelog entry for your changes:

Don't enqueue social logos for Publicize anymore.

Author: ockham

class.jetpack-gutenberg.php

@@ -521,9 +521,5 @@ public static function enqueue_block_editor_assets() {
 		Jetpack::setup_wp_i18n_locale_data();
 
 		wp_enqueue_style( 'jetpack-blocks-editor', $editor_style, array(), $version );
-
-		// The social-logos styles are used for Publicize service icons
-		// TODO: Remove when we ship the icons with the Gutenberg blocks build
-		wp_enqueue_style( 'social-logos' );
 	}
 }