CLEANUP: ebtree: remove another typo, a wrong initialization in insertion code

CLEANUP: ebtree: remove another typo, a wrong initialization in insertion code

(from ebtree 6.0.7)

root_right was wrongly initialized first to <root> which is not the same
type, to be later initialized to root->b[EB_RGHT].

Let's simply remove the wrong and useless initialization.
(cherry picked from commit e63a0c2f56369b52c4d00221d83c2c4569605c06)