add: remove ensure_full_index() with --renormalize

add: remove ensure_full_index() with --renormalize

The --renormalize option updates the EOL conversions for the tracked
files. However, the loop already ignores files marked with the
SKIP_WORKTREE bit, so it will continue to do so with a sparse index
because the sparse directory entries also have this bit set.

Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>