RFR: Moved backport text to backport section

Tue Apr 5 16:01:02 UTC 2022

On Tue, 5 Apr 2022 14:49:29 GMT, Jesper Wilhelmsson <jwilhelm at openjdk.org> wrote:

> Moved "How to fix an incorrect backport creation in JBS" to the backport section. The section is unchanged, only moved. Also some minor improvements (in my mind) to the "JBS Labels" section.

Marked as reviewed by iris (Reviewer).

-------------

PR: https://git.openjdk.java.net/guide/pull/78