[fstream.members] Fix "returns returns".

Author: timsong-cpp

source/iostreams.tex

@@ -9940,7 +9940,7 @@
 \effects
 Calls
 \tcode{rdbuf()->close()}
-and, if that function returns
+and, if that function
 returns a null pointer,
 calls
 \tcode{setstate(\brk{}failbit)}~(\ref{iostate.flags})