Remove unused member function declaration

src/html/chm.cpp

@@ -393,10 +393,6 @@ private:
     // this void* is handle of archive . I'm sorry it is void and not proper
     // type but I don't want to make unzip.h header public.
 
-
-    // locates the file and returns a mspack_file *
-    mspack_file *LocateFile(wxString filename);
-
     // should store pointer to current file
     mspack_file *m_file;