lib: consistent desc. of permitted and excluded subtrees.

Matches language across the `permitted_subtrees` and `excluded_subtrees`
rustdoc comments for the `NameConstraints` struct.

src/lib.rs

@@ -1256,13 +1256,11 @@ impl CertificateParams {
 /// (only relevant for CA certificates)
 #[derive(Debug, PartialEq, Eq, Clone)]
 pub struct NameConstraints {
-	/// If non-empty, a whitelist of subtrees that the
-	/// domain has to match.
+	/// If non-empty, an allow list of subtrees that the domain has to match.
 	pub permitted_subtrees: Vec<GeneralSubtree>,
-	/// A list of excluded subtrees.
+	/// If non-empty, a forbid-list of excluded subtrees that the domain must not match.
 	///
-	/// Any name matching an excluded subtree is invalid
-	/// even if it also matches a permitted subtree.
+	/// Any name matching an excluded subtree is invalid even if it also matches a permitted subtree.
 	pub excluded_subtrees: Vec<GeneralSubtree>,
 }