DEV: Prefer defer_get_set over get/set on DistributedCache (#25967)

lib/stylesheet/manager.rb

@@ -287,9 +287,7 @@ class Stylesheet::Manager
         end
       )
 
-    stylesheets = cache[array_cache_key]
-    return stylesheets if stylesheets.present?
-
+    cache.defer_get_set(array_cache_key) do
       @@lock.synchronize do
         stylesheets = []
 
@@ -329,10 +327,10 @@ class Stylesheet::Manager
           stylesheets << data
         end
 
-      cache.defer_set(array_cache_key, stylesheets.freeze)
         stylesheets
       end
     end
+  end
 
   def color_scheme_stylesheet_details(color_scheme_id = nil, media)
     theme_id = @theme_id || SiteSetting.default_theme_id