Rollup merge of #139802 - Lee-Janggun:fix-allocate-hyperlink, r=workingjubilee

Fix some grammar errors and hyperlinks in doc for `trait Allocator`

I was reading the allocator docs and noticed some weird sentences and missing hyperlink, so I fixed them and made this small PR.

* "while until either" could also be changed to "for a while until either", but I just deleted "while".
* fixed sentence with incorrect "at" and "has/have".
* linked [*currently allocated*] similar to other methods. All other hyperlinks are fine.

Author: GuillaumeGomez