MAINTAINERS: pstore: Remove L: entry

A lot of SoC series end up getting CCed to the hardening list due to
their mention of "pstore" in device tree or similar, and this noise isn't
worth making sure I don't lose pstore patches by having them show up in
the hardening patchwork. ;) I can use better email filters instead!

Link: https://patch.msgid.link/20260116005631.work.387-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>

Author: kees

MAINTAINERS

@@ -20961,7 +20961,6 @@ PSTORE FILESYSTEM
 M:	Kees Cook <kees@kernel.org>
 R:	Tony Luck <tony.luck@intel.com>
 R:	Guilherme G. Piccoli <gpiccoli@igalia.com>
-L:	linux-hardening@vger.kernel.org
 S:	Supported
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/pstore
 F:	Documentation/admin-guide/pstore-blk.rst