GDScript: Allow elements of a parent class in a typed array literal

modules/gdscript/tests/scripts/runtime/errors/typed_array_assign_wrong_to_typed.gd

@@ -0,0 +1,7 @@
+class Foo: pass
+class Bar extends Foo: pass
+class Baz extends Foo: pass
+
+func test():
+	var typed: Array[Bar] = [Baz.new() as Foo]
+	print('not ok')

modules/gdscript/tests/scripts/runtime/errors/typed_array_assign_wrong_to_typed.out

@@ -0,0 +1,7 @@
+GDTEST_RUNTIME_ERROR
+>> ERROR
+>> on function: assign()
+>> core/variant/array.cpp
+>> 222
+>> Method/function failed.
+not ok