rename pink-haired_girl_(majo_no_tabitabi) to houki_(majo_no_tabitabi)

The bulk update request #8167 has been approved by @evazion.

rename pink-haired_girl_(majo_no_tabitabi) -> houki_(majo_no_tabitabi)

Volume 16 - looks like it's her official name (ほうき)

The bulk update request #8167 (forum #201790) has been approved by @evazion.

Please put this source in the wiki if her official name isn't well-known or obvious.