Fix test for Ruby 3.3 (#466)

This test relied on an assumption that is no longer true in 3.3.

spec/dry/types/default_spec.rb

@@ -216,6 +216,13 @@
  context "proc w/o source" do
  let(:value_constructor) { method(:Integer).to_proc }
 
+ before do
+ # Force the source_location to nil, since this specific object's source_location returns a
+ # real value since Ruby 3.3:
+ # ["<internal:kernel>", 305]
+ allow(value_constructor).to receive(:source_location) { nil }
+ end
+
  it "returns string representation of the type" do
  expect(type.to_s).to eql(
  "#<Dry::Types[Default<Nominal<String> "\