[type layout] Clarify size and alignment of pointers to unsized types

Author: joshlf

src/type-layout.md

@@ -58,7 +58,7 @@ r[layout.pointer.thin]
 Pointers to sized types have the same size and alignment as `usize`.
 
 r[layout.pointer.unsized]
-Pointers to unsized types are sized. The size and alignment is guaranteed to be at least equal to the size and alignment of a pointer.
+Pointers to unsized types are sized. The size and alignment of a pointer to an unsized type are guaranteed to be greater than or equal to the size and alignment of a pointer to a sized type.
 
 > [!NOTE]
 > Though you should not rely on this, all pointers to <abbr title="Dynamically Sized Types">DSTs</abbr> are currently twice the size of the size of `usize` and have the same alignment.