Documentation and implementation inconsistency for annotating ink! constructors as payable

[davidsemakula]

While ink! docs "claim" that "ink! constructors are always implicitly payable and thus cannot be flagged as such"
https://use.ink/macros-attributes/payable
https://github.com/paritytech/ink/blob/v4.2.1/crates/ink/macro/src/lib.rs#L316-L317
https://github.com/paritytech/ink/blob/v4.2.1/README.md?plain=1#L233

the ink_ir crate currently accepts payable annotations for ink! constructors
https://github.com/paritytech/ink/blob/v4.2.1/crates/ink/ir/src/ir/item_impl/constructor.rs#L143

Which of these is the right thing to do?

• Update the ink_ir crate to reject ink! payable annotations for ink! constructors.
• Update the docs to remove/rephrase the "thus cannot be flagged as such" part of the claim (e.g. may be replace it with "thus it's redundant to flag them as such").
• Leave as is, it's all intentional.