[Ada] Remove redundant marking of illegal pragma with error posted

[Pierre-Marie de Rodat via Gcc-patches]

We flag illegal pragma Elaborate with a call to Error_Msg on the pragma
argument, which in turn calls Set_Error_Posted on the enclosing
statement, i.e. on the pragma itself. The explicit call to
Set_Error_Posted on the pragma itself was redundant.

Cleanup related to handling of illegal code when detecting uninitialized
scalar objects.

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

gcc/ada/

        * sem_prag.adb (Analyze_Pragma): Remove redundant call to
        Set_Error_Posted.
diff --git a/gcc/ada/sem_prag.adb b/gcc/ada/sem_prag.adb
--- a/gcc/ada/sem_prag.adb
+++ b/gcc/ada/sem_prag.adb
@@ -16008,7 +16008,6 @@ package body Sem_Prag is
                end loop Innr;
 
                if Citem = N then
-                  Set_Error_Posted (N);
                   Error_Pragma_Arg
                     ("argument of pragma% is not withed unit", Arg);
                end if;