FIXUP P2286R8: Remove @\deflibconcept from formattable in synopsis

Author: burblebee

source/utilities.tex

@@ -13495,7 +13495,7 @@
 
   // \ref{format.formattable}, concept \libconcept{formattable}
   template<class T, class charT>
-    concept @\deflibconcept{formattable}@ = @\seebelow@;
+    concept formattable = @\seebelow@;
 
   template<class R, class charT>
     concept @\defexposconcept{const-formattable-range}@ =                                   // \expos