vmalloc: drop Christoph from Reviewers

I haven't been doing as much review as I should.  As part of reducing my
inbox flow drop me from the official Reviewers.  I might still chime in on
patches occasionally.

Link: https://lkml.kernel.org/r/20250224163033.350072-1-hch@lst.de


Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>