instrument-ada_unit.adb: update after a Libadalang API change

TN: V104-012
Change-Id: I90a59564e07bd769ca8e6f2f8902aa9631604c19

Author: pmderodat

tools/gnatcov/instrument-ada_unit.adb

@@ -1796,7 +1796,7 @@ package body Instrument.Ada_Unit is
             Create_Generic_Formal_Type_Decl
               (RC,
                F_Decl    =>
-                 Create_Type_Decl
+                 Create_Formal_Type_Decl
                    (RC,
                     F_Name          =>
                       Make_Defining_Name (UIC, Formal_Type_Name),
@@ -1820,6 +1820,8 @@ package body Instrument.Ada_Unit is
                          F_Has_Limited  =>
                            Make (UIC, Ada_Limited_Present)),
 
+                    F_Default_Type  => No_Node_Rewriting_Handle,
+
                     F_Aspects       => No_Node_Rewriting_Handle),
 
                F_Aspects => No_Node_Rewriting_Handle));