Integrated: Clarified backport docs

[Jesper Wilhelmsson]

On Wed, 20 Aug 2025 18:49:56 GMT, Jesper Wilhelmsson <jwilhelm at openjdk.org> wrote:

> Explaining the difference between jdk21u and jdk21u-dev.

This pull request has now been integrated.

Changeset: a5a7b398
Author:    Jesper Wilhelmsson <jwilhelm at openjdk.org>
URL:       https://git.openjdk.org/guide/commit/a5a7b398ac9583874516f90e1fecb42a8155a94e
Stats:     8 lines in 1 file changed: 3 ins; 2 del; 3 mod

Clarified backport docs

Reviewed-by: iris

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PR: https://git.openjdk.org/guide/pull/158