contributor-guide: be more specific about meta-* trees

* this is often confused to apply for e.g. meta-oe as well
  where it doesn't apply as meta-oe has own ML mentioned
  in README.

(From yocto-docs rev: fd9c078a08933484087e0ce12d4eb0f1d4693995)

Signed-off-by: Martin Jansa <martin.jansa@gmail.com>
Reviewed-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>

documentation/contributor-guide/submit-changes.rst

@@ -432,7 +432,7 @@ varies by component:
    :oe_lists:`bitbake-devel </g/bitbake-devel>`
    mailing list.
 
--  *"meta-\*" trees:* These trees contain Metadata. Use the
+-  *meta-poky* and *meta-yocto-bsp* trees: These trees contain Metadata. Use the
    :yocto_lists:`poky </g/poky>` mailing list.
 
 -  *Documentation*: For changes to the Yocto Project documentation, use the