Remove unnecessary and duplicate paragraph (#2913)

This doesn't belong in a slide, and we already say the same thing at the
top of the slide.

Author: mgeisler

src/user-defined-types/const.md

@@ -4,8 +4,8 @@ minutes: 10
 
 # `const`
 
-Constants are evaluated at compile time and their values are inlined wherever
-they are used:
+Constants are evaluated at compile time and their values are [inlined][1]
+wherever they are used:
 
 <!-- mdbook-xgettext: skip -->
 
@@ -31,8 +31,6 @@ fn main() {
 }
 ```
 
-According to the [Rust RFC Book][1] these are inlined upon use.
-
 Only functions marked `const` can be called at compile time to generate `const`
 values. `const` functions can however be called at runtime.