[cfloat.syn] Update to refer to C23 5.3.5.3.3

... due to new sections added after WG14 N3220

Author: frederick-vs-ja

source/support.tex

@@ -1884,7 +1884,7 @@
 The header \libheader{cfloat} defines all macros the same as
 the C standard library header \libheader{float.h}.
 
-\xrefc{5.2.4.2.2}
+\xrefc{5.3.5.3.3}
 
 \rSec1[support.arith.types]{Arithmetic types}