[Ada] Tune message for illegal aspect Relaxed_Initialization

[Marc Poulhiès via Gcc-patches]

Error message about illegal aspect Relaxed_Initialization was lacking a
whitespace character.

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

gcc/ada/

        * sem_ch13.adb (Analyze_Aspect_Relaxed_Initialization): Fix error
        template.
diff --git a/gcc/ada/sem_ch13.adb b/gcc/ada/sem_ch13.adb
--- a/gcc/ada/sem_ch13.adb
+++ b/gcc/ada/sem_ch13.adb
@@ -2293,7 +2293,7 @@ package body Sem_Ch13 is
                                     then
                                        Error_Msg_Name_1 := Nam;
                                        Error_Msg_N
-                                         ("expression of aspect %" &
+                                         ("expression of aspect % " &
                                           "must be static", Aspect);
                                     end if;