Merge pull request #50531 from wlads/postgresql-guide-fix-enum-syntax

[ci skip] Utilize new `enum` syntax in PostgreSQL guide

(cherry picked from commit 9fc5572)

Author: jonathanhefner

guides/source/active_record_postgresql.md

@@ -274,9 +274,9 @@ end
 ```ruby
 # app/models/article.rb
 class Article < ApplicationRecord
-  enum status: {
+  enum :status, {
     draft: "draft", published: "published"
-  }, _prefix: true
+  }, prefix: true
 end
 ```