MAINTAINERS: fix email address for Lisa Liu

There was a small typographical error which resulted in an
email address which does not exist in Gerrit.  s/lui/liu

(From meta-lenovo rev: 2ad0eb3dac33fc09a8d02d538989c7e96199a0a4)

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ib9fce6b331b2b7e4fb61510044f62bd998afaa4a
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>