[Doc]init deploy readme optimize

[JohnTeslaa]

Purpose of this pull request

Check list

• Code changed are covered with tests, or it does not need tests for reason:
• If any new Jar binary package adding in your PR, please add License Notice according
  New License Guide
• If necessary, please update the documentation to describe the new feature. https://github.com/apache/seatunnel/tree/dev/docs

[JohnTeslaa]

if too short, will be an error like : The signing key's size is 72 bits which is not secure enough for the HS256 algorithm.

[arshadmohammad]

LGTM +1