Fix typo in v14 metadata parser

[HolyGrease]

Description

Fix typo in metadata parser.

For example chain contains event like so:

pub enum Event<T: Config> {
  AccountUpdated {
    account_id: T::AccountId,
    username: T::Username,
    new_username: Option<T::Username>,
    phone_number_hash: T::PhoneNumberHash,
    new_phone_number_hash: Option<T::PhoneNumberHash>,
  },
  // ...
}

Now after decoding chain events you get something like this, where instead of field names uses field types:

{
  T::AccountId: ...,
  T::Username: ...,
  // ...
}

But the actual value should be:

{
  account_id: ...,
  username: ...,
  // ...
}

[Lohann]

@HolyGrease Thank you very much for the contribution! Seems some units tests are failling, if you want to run only the unit tests of substrate_metadata package, you can do this:

dart run melos exec --scope="substrate_metadata"  -- 'dart test'

[justkawal]

Closing this as no followup is taken and everything already seems to be working fine without the typo.