MAINTAINERS: adjust file entry in MAPLE TREE

Commit 0f3b602e1bad ("tools: separate out shared radix-tree components")
moves files from radix-tree/linux to shared/linux in the ./tools/testing/
directory, but misses to adjust a file entry in MAPLE TREE.  Hence,
./scripts/get_maintainer.pl --self-test=patterns complains about a broken
reference.

Adjust the file entry in MAPLE TREE.

Link: https://lkml.kernel.org/r/20250312105245.216302-1-lukas.bulwahn@redhat.com


Signed-off-by: Lukas Bulwahn <lukas.bulwahn@redhat.com>
Acked-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>