Fix a string interpolation deprecated issue on the `WPCOM_Liveblog_En…

…try_Extend_Feature_Commands` class

classes/class-wpcom-liveblog-entry-extend-feature-commands.php

@@ -240,7 +240,7 @@ public function do_action_per_type( $id, $post_id ) {
 
 			// Run the command_after action on the
 			// content for the current type.
-			do_action( "liveblog_command_${type}_after", $content, $id, $post_id );
+			do_action( "liveblog_command_{$type}_after", $content, $id, $post_id );
 		}
 	}