[cfloat.syn] Fix macro definition to be long, not int.

This was a misapplication of P3348R4.
Checked that the C standard also uses long.

Author: tkoeppe

source/support.tex

@@ -1835,7 +1835,7 @@
 \indexheader{cfloat}%
 \begin{codeblock}
 // all freestanding
-#define __STDC_VERSION_FLOAT_H__ 202311
+#define __STDC_VERSION_FLOAT_H__ 202311L
 
 #define @\libmacro{FLT_ROUNDS}@ @\seebelow@
 #define @\libmacro{FLT_EVAL_METHOD}@ @\seebelow@