MAINTAINERS: fix Pantelis Antoniou email address

Trivial fix (unless Pantelis has a new email address):

Pantelis Antoniou <panto.antoniou-consulting.com>
                        ^
make it:
Pantelis Antoniou <panto@antoniou-consulting.com>

Signed-off-by: Igor Grinberg <grinberg@compulab.co.il>
Cc: Pantelis Antoniou <panto@antoniou-consulting.com>