Qualifying Saber

BUR #496 has been approved by @user_2.

create alias saber -> saber_(fate)

Related: https://danbooru.donmai.us/forum_topics/19339 & https://danbooru.donmai.us/forum_topics/25375

We have this problem in AIBooru that we have the original Saber tag. However, saber_(fate)_(cosplay) implicates saber_(fate), so now we have both tags existing. For other reasons to alias, refer to the Danbooru topics above.

The bulk update request #496 (forum #3111) has been approved by @Penance.

IMO the alias should not remain (it's still ambiguous), but given the popularity I'm not sure it should be removed immediately. This site is smaller than Danbooru so the potential effect is smaller, but still.