[execution.syn] Remove meaningless subclause comments

Author: tkoeppe

source/exec.tex

@@ -667,7 +667,6 @@
   inline constexpr spawn_future_t @\libglobal{spawn_future}@{};
 
   // \ref{exec.util}, sender and receiver utilities
-  // \ref{exec.util.cmplsig}
   template<class Fn>
     concept @\exposconceptnc{completion-signature}@ = @\seebelownc@;                   // \expos
 
@@ -677,7 +676,6 @@
   template<class Sigs>
     concept @\exposconceptnc{valid-completion-signatures}@ = @\seebelownc@;            // \expos
 
-  // \ref{exec.util.cmplsig.trans}
   template<
     @\exposconcept{valid-completion-signatures}@ InputSignatures,
     @\exposconcept{valid-completion-signatures}@ AdditionalSignatures = completion_signatures<>,
@@ -725,7 +723,6 @@
   template<@\exposconcept{class-type}@ Promise>
     struct with_awaitable_senders;
 
-  // \ref{exec.scope}
   // \ref{exec.scope.concepts}, scope concepts
   template<class Token>
     concept @\libconcept{scope_token}@ = @\seebelow@;