MAINTAINERS: remove Alexander Graf from EFI PAYLOAD

The last review by Alex was in 2019.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index 6ae81c5..38c68ee 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -737,7 +737,6 @@
 
 EFI PAYLOAD
 M:	Heinrich Schuchardt <xypron.glpk@gmx.de>
-R:	Alexander Graf <agraf@csgraf.de>
 S:	Maintained
 T:	git https://source.denx.de/u-boot/custodians/u-boot-efi.git
 F:	doc/api/efi.rst