test: use MyMockModule for testing parent-module

Author: ven-k

test/model_parsing.jl

@@ -590,14 +590,6 @@ end
     @test getdefault(component.written_out_for_2.sc) == 3
 end
 
-module GetParentModule
-
-using ModelingToolkit
-
-@mtkmodel Component begin end
-
-end
-
 @testset "Parent module of Models" begin
-    @test parentmodule(GetParentModule.Component) == GetParentModule
+    @test parentmodule(MyMockModule.Ground) == MyMockModule
 end