MAINTAINERS: use tabs for indent of CONFIDENTIAL COMPUTING THREAT MODEL

There are two MAINTAINERS entries which snuck in during the previous
merge window which use spaces instead of tabs for indent. The rest
of the file uses tabs. Fix CONFIDENTIAL COMPUTING THREAT MODEL FOR
X86 VIRTUALIZATION (SNP/TDX).

Given the prevalence of using tabs some scripts (AKA my scripts)
assume tabs when parsing.

The faulty entry was added in commit 1f597b1a ("docs: security:
Confidential computing intro and threat model for x86 virtualization")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Carlos Bilbao <carlos.bilbao@amd.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240103160938.1006517-1-kuba@kernel.org