[special.mem.concepts] Fixed misspelled "sized_sentinel_for".

This was a misapplication of P3179R9.

Author: tkoeppe

source/algorithms.tex

@@ -13593,7 +13593,7 @@
 template<class S, class I>
 concept @\defexposconcept{nothrow-sized-sentinel-for}@ = // \expos
   @\exposconcept{nothrow-sentinel-for}@<S, I> &&
-  @\libconcept{sentinel_for}@<S, I>;
+  @\libconcept{sized_sentinel_for}@<S, I>;
 \end{itemdecl}
 
 \begin{itemdescr}