LWG3313 join_view::iterator::operator-- is incorrectly constrained

Also fixes NB US 294 (C++20 CD).

Author: Dawn Perchik

source/ranges.tex

@@ -4790,11 +4790,13 @@
 
     constexpr @\exposid{iterator}@& operator--()
       requires @\exposid{ref-is-glvalue}@ && bidirectional_range<@\exposid{Base}@> &&
-               bidirectional_range<range_reference_t<@\exposid{Base}@>>;
+               bidirectional_range<range_reference_t<@\exposid{Base}@>> &&
+               common_range<range_reference_t<@\exposid{Base}@>>;
 
     constexpr @\exposid{iterator}@ operator--(int)
       requires @\exposid{ref-is-glvalue}@ && bidirectional_range<@\exposid{Base}@> &&
-               bidirectional_range<range_reference_t<@\exposid{Base}@>>;
+               bidirectional_range<range_reference_t<@\exposid{Base}@>> &&
+               common_range<range_reference_t<@\exposid{Base}@>>;
 
     friend constexpr bool operator==(const @\exposid{iterator}@& x, const @\exposid{iterator}@& y)
       requires @\exposid{ref-is-glvalue}@ && equality_comparable<iterator_t<@\exposid{Base}@>> &&
@@ -4985,7 +4987,8 @@
 \begin{itemdecl}
 constexpr @\exposid{iterator}@& operator--()
   requires @\exposid{ref-is-glvalue}@ && bidirectional_range<@\exposid{Base}@> &&
-           bidirectional_range<range_reference_t<@\exposid{Base}@>>;
+           bidirectional_range<range_reference_t<@\exposid{Base}@>> &&
+           common_range<range_reference_t<@\exposid{Base}@>>;
 \end{itemdecl}
 
 \begin{itemdescr}
@@ -5006,7 +5009,8 @@
 \begin{itemdecl}
 constexpr @\exposid{iterator}@ operator--(int)
   requires @\exposid{ref-is-glvalue}@ && bidirectional_range<@\exposid{Base}@> &&
-           bidirectional_range<range_reference_t<@\exposid{Base}@>>;
+           bidirectional_range<range_reference_t<@\exposid{Base}@>> &&
+           common_range<range_reference_t<@\exposid{Base}@>>;
 \end{itemdecl}
 
 \begin{itemdescr}