[cstdio.syn, cwctype.syn] Fix cross references to C

Author: tkoeppe

source/iostreams.tex

@@ -18998,7 +18998,7 @@
 introduce a data race\iref{res.on.data.races} with other calls to \tcode{tmpnam} with
 an argument that is a null pointer value.
 
-\xrefc{7.21}
+\xrefc{7.23}
 
 \rSec2[cinttypes.syn]{Header \tcode{<cinttypes>} synopsis}
 

source/text.tex

@@ -13088,7 +13088,7 @@
 The contents and meaning of the header \libheaderdef{cwctype}
 are the same as the C standard library header \libheader{wctype.h}.
 
-\xrefc{7.30}
+\xrefc{7.32}
 
 \rSec2[cwchar.syn]{Header \tcode{<cwchar>} synopsis}