Update bridge-searching-online.md

[meetthehorizon]

a = find_2ecc(a) is called in the add_edge function, then again in the make_root(int v) function as the first line which is redundant.

[adamant-pwn]

Yeah, I suppose unless someone uses make_root independently from add_edge, it's unlikely to have any side effects. And also semantically makes somewhat more sense without find_2ecc call. Thanks!