[alg.find.first.of] Rename subclause title

Fixes US 158-256 26.6.9 (C+26 CD)

Fixes cplusplus/nbballot#831.

Author: AlisdairM

source/algorithms.tex

@@ -1197,7 +1197,7 @@
                  Proj1 proj1 = {}, Proj2 proj2 = {});           // freestanding-deleted
   }
 
-  // \ref{alg.find.first.of}, find first
+  // \ref{alg.find.first.of}, find first of
   template<class InputIterator, class ForwardIterator>
     constexpr InputIterator
       find_first_of(InputIterator first1, InputIterator last1,
@@ -5215,7 +5215,7 @@
 applications of the corresponding predicate and any projections.
 \end{itemdescr}
 
-\rSec2[alg.find.first.of]{Find first}
+\rSec2[alg.find.first.of]{Find first of}
 
 \indexlibraryglobal{find_first_of}%
 \begin{itemdecl}