[istream.syn,ostream.syn] update synopses according to LWG1203 (#4084)

Edits missed by commit ffb23d0.

Author: frederick-vs-ja

source/iostreams.tex

@@ -4067,8 +4067,8 @@
   template<class charT, class traits>
     basic_istream<charT, traits>& ws(basic_istream<charT, traits>& is);
 
-  template<class charT, class traits, class T>
-    basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>&& is, T&& x);
+  template<class Istream, class T>
+    Istream&& operator>>(Istream&& is, T&& x);
 }
 \end{codeblock}
 
@@ -4102,8 +4102,8 @@
   template<class charT, class traits>
     basic_ostream<charT, traits>& flush_emit(basic_ostream<charT, traits>& os);
 
-  template<class charT, class traits, class T>
-    basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>&& os, const T& x);
+  template<class Ostream, class T>
+    Ostream&& operator<<(Ostream&& os, const T& x);
 }
 \end{codeblock}