[Ada] Fix use of single question mark in error message

[Pierre-Marie de Rodat]

Single question marks are deprecated.

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

gcc/ada/

        * exp_prag.adb (Expand_Pragma_Inspection_Point): Fix error
        message.
diff --git a/gcc/ada/exp_prag.adb b/gcc/ada/exp_prag.adb
--- a/gcc/ada/exp_prag.adb
+++ b/gcc/ada/exp_prag.adb
@@ -2413,7 +2413,7 @@ package body Exp_Prag is
          if Present (Freeze_Node (Entity (Expression (Assoc)))) and then
            not Is_Frozen (Entity (Expression (Assoc)))
          then
-            Error_Msg_NE ("?inspection point references unfrozen object &",
+            Error_Msg_NE ("??inspection point references unfrozen object &",
               Assoc,
               Entity (Expression (Assoc)));
             Remove_Inspection_Point := True;