[exec.snd.expos] Move Remarks into itemdescr

Author: timsong-cpp

source/exec.tex

@@ -1713,13 +1713,13 @@
 type \tcode{\exposid{basic-sender}<Tag, decay_t<Data>, decay_t<Child>...>}
 that has been direct-list-initialized with the forwarded arguments,
 where \exposid{basic-sender} is the following exposition-only class template except as noted below.
-\end{itemdescr}
 
 \pnum
 \remarks
 The default template argument for the \tcode{Data} template parameter
 denotes an unspecified empty trivially copyable class type
 that models \libconcept{semiregular}.
+\end{itemdescr}
 
 \begin{codeblock}
 namespace std::execution {