fixup: use proper indentation after template header

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

Author: dietmarkuehl

source/exec.tex

@@ -5999,7 +5999,7 @@
   class task {
     // \ref{task.state}
     template<@\libconcept{receiver}@ Rcvr>
-    class @\exposidnc{state}@; // \expos
+      class @\exposidnc{state}@;   // \expos
 
   public:
     using sender_concept = sender_t;