MAINTAINERS: ena: remove Zorik Machulsky from reviewers

While ENA has 3 reviewers and 2 maintainers, we mostly see review
tags and comments from the maintainers. While we very much appreciate
Zorik's invovment in the community let's trim the reviewer list
down to folks we've seen tags from.

Subsystem AMAZON ETHERNET DRIVERS
  Changes 13 / 269 (4%)
  Last activity: 2020-11-24
  Netanel Belgazal <netanel@amazon.com>:
    Author 24dee0c7 2019-12-10 00:00:00 43
    Tags 0e3a3f6d 2020-07-21 00:00:00 47
  Arthur Kiyanovski <akiyano@amazon.com>:
    Author 0e3a3f6d 2020-07-21 00:00:00 79
    Tags 09323b3b 2020-11-24 00:00:00 104
  Guy Tzalik <gtzalik@amazon.com>:
    Tags 713865da 2020-09-10 00:00:00 3
  Saeed Bishara <saeedb@amazon.com>:
    Tags 470793a7

 2020-02-11 00:00:00 2
  Zorik Machulsky <zorik@amazon.com>:
  Top reviewers:
    [4]: sameehj@amazon.com
    [3]: snelson@pensando.io
    [3]: shayagr@amazon.com
  INACTIVE MAINTAINER Zorik Machulsky <zorik@amazon.com>

Signed-off-by: Jakub Kicinski <kuba@kernel.org>