LWG4205 let_[*].transform_env is specified in terms of the let_* sender itself instead of its child

[exec.let] Added : before codeblock for consistency.

Author: burblebee

source/exec.tex

@@ -3612,8 +3612,11 @@
 is \tcode{false},
 then the expression \tcode{\exposid{let-cpo}.transform_env(sndr, env)}
 is ill-formed.
-Otherwise, it is equal to
-\tcode{\exposid{JOIN-ENV}(\exposid{let-env}(sndr), \exposid{FWD-ENV}(env))}.
+Otherwise, it is equal to:
+\begin{codeblock}
+auto& [_, _, child] = sndr;
+return @\exposid{JOIN-ENV}@(@\exposid{let-env}@(child), @\exposid{FWD-ENV}@(env));
+\end{codeblock}
 
 \pnum
 Let the subexpression \tcode{out_sndr} denote