docs: fix delay message type casing

[titanniya542-spec]

Summary

• Update the delay message topic creation example to use +message.type=DELAY.
• This makes the example consistent with the later mqadmin example on the same page.

Fixes #744.

Testing

• rg -n "message\.type=Delay|message\.type=DELAY" i18n\en\docusaurus-plugin-content-docs\version-5.0\04-featureBehavior\02delaymessage.md
• git diff --check

AI disclosure

This pull request was prepared with assistance from OpenAI Codex.