maple_tree: mtree_insert*: fix typo in kernel-doc description

Replace "Insert and entry at a give index" with "Insert an entry at a
given index"

Link: https://lkml.kernel.org/r/20230715143920.994812-1-rppt@kernel.org


Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>