Migrated styles for "share" plugin to new platform (elastic#59981)

Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>

src/legacy/ui/public/_index.scss

@@ -15,7 +15,6 @@
 @import './error_url_overflow/index';
 @import './exit_full_screen/index';
 @import './field_editor/index';
-@import './share/index';
 @import './style_compile/index';
 @import '../../../plugins/management/public/components/index';
 

src/plugins/share/public/index.scss

@@ -0,0 +1 @@
+@import './components/index'

src/plugins/share/public/plugin.ts

@@ -17,6 +17,8 @@
  * under the License.
  */
 
+import './index.scss';
+
 import { CoreSetup, CoreStart, Plugin } from 'src/core/public';
 import { ShareMenuManager, ShareMenuManagerStart } from './services';
 import { ShareMenuRegistry, ShareMenuRegistrySetup } from './services';