remove stuff about #define

This obscures more than it helps.

Fixes #25573

Author: steveklabnik

src/doc/trpl/const-and-static.md

@@ -78,7 +78,3 @@ Almost always, if you can choose between the two, choose `const`. It’s pretty
 rare that you actually want a memory location associated with your constant,
 and using a const allows for optimizations like constant propagation not only
 in your crate but downstream crates.
-
-A const can be thought of as a `#define` in C: it has metadata overhead but it
-has no runtime overhead. “Should I use a #define or a static in C,” is largely
-the same question as whether you should use a const or a static in Rust.