fix(sol-macro): remove #[automatically_derived] from non-trait impls

[DaniPopes]

This triggers an unused_attributes warning in the latest stable version.

warning: `#[automatically_derived]` attribute cannot be used on inherent impl blocks
 --> src/main.rs:4:1
  |
4 | #[automatically_derived]
  | ^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
  = help: `#[automatically_derived]` can only be applied to trait impl blocks
  = note: `#[warn(unused_attributes)]` (part of `#[warn(unused)]`) on by default