docs: use fiber blocking terminology

[MahishaKannan]

No description provided.

[reardonj]

@MahishaKannan , I take it this is an attempt to address #4597 ? You'll want to search for usages of "semantically" as well and update those usages (probably by just dropping the "semantically" in most cases)

e.g.

cats-effect/docs/std/dequeue.md

Line 41 in de84c01

`offer` may semantically block if the pqueue is already full. `take` is

[MahishaKannan]

Thanks for the feedback! I've searched the documentation for usages of “semantically” and updated the blocking-related descriptions, leaving unrelated uses unchanged.