confirmation_active documentation has mistakes

[dsiganos]

The documentation of confirmation_active has a couple of problems:

It refers to qualified roots as roots. But roots are not the same as qualified roots, we should use their proper name, qualified roots.

It says that the qualified root for an open block is:
0000000000000000000000000000000000000000000000000000000000000000 + account public key
whereas it is:
account public key + 0000000000000000000000000000000000000000000000000000000000000000