lang: Use AccountDeserialize when deserializing accounts with `Acco…

…unt` utils (#3213)

lang/attribute/program/src/declare_program/mods/utils.rs

@@ -27,10 +27,9 @@ fn gen_account(idl: &Idl) -> proc_macro2::TokenStream {
  let if_statements = idl.accounts.iter().map(|acc| {
  let name = format_ident!("{}", acc.name);
  let disc = gen_discriminator(&acc.discriminator);
- let disc_len = acc.discriminator.len();
  quote! {
  if value.starts_with(&#disc) {
- return #name::try_from_slice(&value[#disc_len..])
+ return #name::try_deserialize_unchecked(&mut &value[..])
  .map(Self::#name)
  .map_err(Into::into)
  }