contributor-guide/submit-changes.rst: suggest to remove the git signature

By default when sending patches Git adds the git version at the bottom
of the patch, which is not necessary in most cases. Suggest to remove it
when configuring Git when sending patches.

Suggested-By: Jaekyu Lee <jaekyu.lee@lge.com>
(From yocto-docs rev: d3465691231f10466703198a831a681803ffdfad)

Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/contributor-guide/submit-changes.rst

@@ -65,6 +65,13 @@ use to identify your commits::
    git config --global user.name "Ada Lovelace"
    git config --global user.email "ada.lovelace@gmail.com"
 
+By default, Git adds a signature line at the end of patches containing the Git
+version. We suggest to remove it as it doesn't add useful information.
+
+Remove it with the following command::
+
+   git config --global format.signature ""
+
 Clone the Git repository for the component to modify
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