const_eval.md: use sentence case for section title, for consistency
diff --git a/src/const_eval.md b/src/const_eval.md
index ce6cc59..fa6b8d6 100644
--- a/src/const_eval.md
+++ b/src/const_eval.md
@@ -256,7 +256,7 @@
 generics.
 
 r[const-eval.const-fn]
-## Const Functions
+## Const functions
 
 r[const-eval.const-fn.general]
 A _const fn_ is a function that one is permitted to call from a const context.