[range.join.iterator] Remove spurious return (#8038)

Author: hewillk

source/ranges.tex

@@ -7091,7 +7091,7 @@
 \begin{itemdescr}
 \pnum
 \effects
-Equivalent to: \tcode{return ranges::iter_swap(*x.\exposid{inner_}, *y.\exposid{inner_});}
+Equivalent to: \tcode{ranges::iter_swap(*x.\exposid{inner_}, *y.\exposid{inner_});}
 \end{itemdescr}
 
 \rSec3[range.join.sentinel]{Class template \tcode{join_view::\exposid{sentinel}}}