fixup: use proper indentation after template.

Co-authored-by: Jan Schultke <[email protected]>

Author: dietmarkuehl

source/exec.tex

@@ -5912,7 +5912,7 @@
   using sender_concept = sender_t;
 
   template<@\libconcept{receiver}@ Rcvr>
-  @\exposid{state}@<Rcvr> connect(Rcvr&& rcvr);
+    @\exposid{state}@<Rcvr> connect(Rcvr&& rcvr);
 };
 \end{codeblock}