MAINTAINERS: remove Laszlo Ersek's entries

I've relinquished my edk2 roles with the following commit message [1] [2]
[3]:

> Maintainers.txt: remove Laszlo Ersek's entries
>
> I'm relinquishing all my roles listed in "Maintainers.txt", for personal
> reasons.
>
> My email address <lersek@redhat.com> remains functional.
>
> To my understanding, my employer is working to assign others engineers
> to the edk2 project (at their discretion).

[1] https://edk2.groups.io/g/devel/message/77585
[2] https://listman.redhat.com/archives/edk2-devel-archive/2021-July/msg00202.html
[3] http://mid.mail-archive.com/20210708070916.8937-1-lersek@redhat.com

Accordingly, remove my entries from QEMU's MAINTAINERS file as well, which
all relate to guest firmware.

Cc: Daniel P. Berrange <berrange@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Kashyap Chamarthy <kchamart@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20210708071409.9671-1-lersek@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

MAINTAINERS

@@ -2202,7 +2202,6 @@ F: include/hw/southbridge/piix.h
 
 Firmware configuration (fw_cfg)
 M: Philippe Mathieu-Daudé <philmd@redhat.com>
-R: Laszlo Ersek <lersek@redhat.com>
 R: Gerd Hoffmann <kraxel@redhat.com>
 S: Supported
 F: docs/specs/fw_cfg.txt
@@ -2934,15 +2933,13 @@ F: include/hw/i2c/smbus_slave.h
 F: include/hw/i2c/smbus_eeprom.h
 
 Firmware schema specifications
-M: Laszlo Ersek <lersek@redhat.com>
 M: Philippe Mathieu-Daudé <philmd@redhat.com>
 R: Daniel P. Berrange <berrange@redhat.com>
 R: Kashyap Chamarthy <kchamart@redhat.com>
 S: Maintained
 F: docs/interop/firmware.json
 
 EDK2 Firmware
-M: Laszlo Ersek <lersek@redhat.com>
 M: Philippe Mathieu-Daudé <philmd@redhat.com>
 S: Supported
 F: hw/i386/*ovmf*