Maintainers.txt: remove Laszlo Ersek's entries

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).

Cc: Andrew Fish <afish@apple.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Philippe Mathieu-Daud? <philmd@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Andrew Fish <afish@apple.com>
Reviewed-by: Leif Lindholm <leif@nuviainc.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>