MAINTAINERS: Drop the lines with Sarah Harris

MAINTAINERS: Drop the lines with Sarah Harris

In a mail to the qemu-devel mailing list, Sarah wrote:

"I was added as a reviewer (in MAINTAINERS) for the AVR target for the
 duration of my research work using it.
 The funding for my project expires in the middle of April, so I will not be
 able to provide time for reviewing patches from that point."

Thus let's remove the corresponding lines in the MAINTAINERS file.

Message-Id: <20210401062426.3192118-1-thuth@redhat.com>
Reviewed-by: Sarah Harris <S.E.Harris@kent.ac.uk>
Signed-off-by: Thomas Huth <thuth@redhat.com>