[defns.order.ptr] Add missing hypen in "built-in"

Author: tkoeppe

source/intro.tex

@@ -321,7 +321,7 @@
 \impldef{strict total order over pointer values}
 strict total ordering over all pointer values
 such that the ordering is consistent with the partial order
-imposed by the builtin operators
+imposed by the built-in operators
 \tcode{<}, \tcode{>}, \tcode{<=}, \tcode{>=}, and \tcode{<=>}
 
 \indexdefn{limits!implementation}%