[foreign-jextract] Integrated: Update README

[Maurizio Cimadamore]

On Wed, 2 Dec 2020 16:28:44 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> I've tweaked the README file of the foreign-jextract branch to reflect the changes in the branch organization of the repository.

This pull request has now been integrated.

Changeset: 1a8fa7ac
Author:    Maurizio Cimadamore <mcimadamore at openjdk.org>
URL:       https://git.openjdk.java.net/panama-foreign/commit/1a8fa7ac
Stats:     4 lines in 1 file changed: 0 ins; 1 del; 3 mod

Update README

Reviewed-by: jvernee

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PR: https://git.openjdk.java.net/panama-foreign/pull/405