[ifstream.members] Remove mistakenly added @

Author: frederick-vs-ja

source/iostreams.tex

@@ -11958,7 +11958,7 @@
 \begin{itemdescr}
 \pnum
 \returns
-\tcode{const_cast<basic_filebuf<charT, traits>*>(addressof(@\exposid{sb}@))}.
+\tcode{const_cast<basic_filebuf<charT, traits>*>(addressof(\exposid{sb}))}.
 \end{itemdescr}
 
 \indexlibrarymember{native_handle}{basic_ifstream}%