I no longer say "polymorphic" since it's a bit ambiguous here.

This reverts commit 7e2548f.

Now I know why it was redefined: it seems like it's potentially because
of the orphan rule. Here are the error messages:

error[E0119]: conflicting implementations of trait `std::fmt::Debug` for type `!`:
 --> src/primitive_docs.rs:236:1
  |
6 | impl Debug for ! {
  | ^^^^^^^^^^^^^^^^
  |
  = note: conflicting implementation in crate `core`:
          - impl std::fmt::Debug for !;

error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
 --> src/primitive_docs.rs:236:1
  |
6 | impl Debug for ! {
  | ^^^^^^^^^^^^^^^-
  | |              |
  | |              `!` is not defined in the current crate
  | impl doesn't use only types from inside the current crate
  |
  = note: define and implement a trait or new type instead

Co-authored-by: Joshua Nelson <joshua@yottadb.com>