Move semantic/abstract docs to the semantic module

The comment on why we use semantic and abstract interchangeable is
better placed in the `semantic` module docs.

Author: tcharding

src/policy/mod.rs

@@ -20,8 +20,6 @@ pub mod concrete;
 pub mod semantic;
 
 pub use self::concrete::Policy as Concrete;
-/// Semantic policies are "abstract" policies elsewhere; but we
-/// avoid this word because it is a reserved keyword in Rust
 pub use self::semantic::Policy as Semantic;
 use crate::descriptor::Descriptor;
 use crate::miniscript::{Miniscript, ScriptContext};

src/policy/semantic.rs

@@ -2,6 +2,9 @@
 // SPDX-License-Identifier: CC0-1.0
 
 //! Abstract Policies
+//!
+//! We use the term "semantic" for abstract policies because "abstract" is
+//! a reserved keyword in Rust.
 
 use core::str::FromStr;
 use core::{fmt, str};