[fs.race.behavior] Fix cross-reference to self (#4122)

Author: JohelEGP

source/iostreams.tex

@@ -11383,7 +11383,7 @@
 when multiple threads, processes, or computers interleave access and
 modification of
 the same object within a file system.
-Behavior is undefined if calls to functions provided by subclause~\ref{fs.race.behavior} introduce a file system race.
+Behavior is undefined if calls to functions provided by subclause~\ref{filesystems} introduce a file system race.
 
 \pnum
 If the possibility of a file system race would make it unreliable for a