[thread.thread.id] Remove extraneous space in operator<< declaration

Author: Andreas-Krug

source/threads.tex

@@ -1587,7 +1587,7 @@
 \begin{itemdecl}
 template<class charT, class traits>
   basic_ostream<charT, traits>&
-    operator<< (basic_ostream<charT, traits>& out, thread::id id);
+    operator<<(basic_ostream<charT, traits>& out, thread::id id);
 \end{itemdecl}
 
 \begin{itemdescr}