fxup: add proper indentation after template head

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

Author: dietmarkuehl

source/exec.tex

@@ -6017,7 +6017,7 @@
     ~task();
 
     template<@\libconcept{receiver}@ Rcvr>
-    @\exposid{state}@<Rcvr> connect(Rcvr&& rcvr);
+      @\exposid{state}@<Rcvr> connect(Rcvr&& rcvr);
 
   private:
     coroutine_handle<promise_type> @\exposidnc{handle}@; // \expos