deprecate `#[pallet::generate_storage_info]`

[kianenigma]

As it seems to be the default now.

we have both pallet#generate_storage_info and `pallet::without_storage_info.
one must to be redundant.

Will assign to Oliver to make the final call about what should be the default, but can be done by anyone.

[ggwpez]

It looks like this is not valid pallet syntax, so just the docs are wrong. It only works for V1 decl_module syntax.

#[pallet::pallet]
#[pallet::generate_storage_info]
pub struct Pallet<T>(_);

Does not compile with expected one of: generate_store, without_storage_info, storage_version.
So i guess we dont need to deprecate anything, just clean the docs.