gdbsupport: remove unecessary template on iterator_range constructor

This is a copy-pasto.

Change-Id: I947772f6a694b33e393762dbf2931ebe2031c1c5

gdbsupport/iterator-range.h

@@ -36,7 +36,6 @@ struct iterator_range
   {}
 
   /* Create an iterator range using explicit BEGIN and END iterators.  */
-  template <typename... Args>
   iterator_range (IteratorType begin, IteratorType end)
     : m_begin (std::move (begin)), m_end (std::move (end))
   {}