MAINTAINERS: remove myself as RISCV reviewer

I haven't been actively reviewing Xen RISC-V patches for several years,
so remove myself from the reviewer list to better reflect the current
reality. The RISC-V port has come a long way thanks to Oleksii, current
contributors, and maintainers, and it has been exciting to see. Many
thanks to everyone, I hope we cross paths again in the future!

Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>

MAINTAINERS

@@ -506,7 +506,6 @@ F:	tools/hotplug/Linux/block-drbd-probe
 
 RISCV
 R:	Alistair Francis <alistair.francis@wdc.com>
-R:	Bob Eshleman <bobbyeshleman@gmail.com>
 R:	Connor Davis <connojdavis@gmail.com>
 R:	Oleksii Kurochko <oleksii.kurochko@gmail.com>
 S:	Supported