chore: rename HashMap.remove to HashMap.erase

[TwoFX]

The name remove was chosen because it is more popular in mainstream programming languages, but being consistent with other Lean container types (including Lean.HashMap and Batteries.HashMap) is more important, so let's change the name while we still can.

[leanprover-community-mathlib4-bot]

Mathlib CI status (docs):

• ❗ Batteries/Mathlib CI will not be attempted unless your PR branches off the nightly-with-mathlib branch. Try git rebase 31de2494fb603081d261a5ded574b7c2f884c755 --onto ce73bbe277140201cdb3ad3015c13d01948704b2. (2024-07-16 07:32:42)
• ❗ Batteries/Mathlib CI will not be attempted unless your PR branches off the nightly-with-mathlib branch. Try git rebase 7aec6c9ae7a54935ada0df0b4cc1efafc2291007 --onto ce73bbe277140201cdb3ad3015c13d01948704b2. (2024-07-16 08:14:26)