argo: fall back maintainership into the rest

Due to unresponsiveness of the current maintainer.  In particular, the
committers have been trying to get in touch with Christopher for 2 weeks to
have a chat about disputes around recent commits and pending changes to the
ARGO component without getting any response.

Signed-of-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
Acked-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Anthony PERARD <anthony.perard@vates.tech>

MAINTAINERS

@@ -241,7 +241,6 @@ F:	xen/arch/x86/hvm/svm/
 F:	xen/arch/x86/include/asm/hvm/svm/
 
 ARGO
-M:	Christopher Clark <christopher.w.clark@gmail.com>
 R:	Daniel P. Smith <dpsmith@apertussolutions.com>
 S:	Maintained
 F:	xen/include/public/argo.h