[Ada] Fix the Ada 2022 iterated component association RM reference

[Pierre-Marie de Rodat via Gcc-patches]

Fix the error message pointing to the Ada reference section on mixed
iterated component association being forbidden.  Remove useless loop.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

        * sem_aggr.adb (Resolve_Array_Aggregate): Fix ARM reference.
        Remove useless loop.
diff --git a/gcc/ada/sem_aggr.adb b/gcc/ada/sem_aggr.adb
--- a/gcc/ada/sem_aggr.adb
+++ b/gcc/ada/sem_aggr.adb
@@ -1833,7 +1833,7 @@ package body Sem_Aggr is
                  or else No (Iterator_Specification (Assoc))
                then
                   Error_Msg_N ("mixed iterated component association"
-                   & " (RM 4.4.3 (17.1/5))",
+                   & " (RM 4.3.3 (17.1/5))",
                       Assoc);
                   return False;
                end if;
@@ -1852,7 +1852,7 @@ package body Sem_Aggr is
                  and then Present (Iterator_Specification (Assoc))
                then
                   Error_Msg_N ("mixed iterated component association"
-                    & " (RM 4.4.3 (17.1/5))",
+                    & " (RM 4.3.3 (17.1/5))",
                       Assoc);
                   return False;
                end if;
@@ -1860,9 +1860,6 @@ package body Sem_Aggr is
                Next (Assoc);
             end loop;
 
-            while Present (Assoc) loop
-               Next (Assoc);
-            end loop;
          end if;
 
          Assoc := First (Component_Associations (N));