update(README): amend 'owners' section (DefinitelyTyped#55397)

Add TL;DR with explicit intruction to not modify autogenerated
codeowners file.

Thanks!

Author: peterblazejewicz

README.md

@@ -31,7 +31,6 @@ and [Japanese](https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/RE
 * [FAQ](#faq)
 * [License](#license)
 
-
 ## Current status
 
 This section tracks the health of the repository and publishing process.
@@ -402,6 +401,8 @@ If a file is neither tested nor referenced in `index.d.ts`, add it to a file nam
 
 ### Definition owners
 
+> TL;DR: do not modify `.github/CODEOWNERS`, always modify list of the owners in the `index.d.ts` header
+
 DT has the concept of "Definition Owners" which are people who want to maintain the quality of a particular module's types
 
 * Adding yourself to the list will cause you to be notified (via your GitHub username) whenever someone makes a pull request or issue about the package.