Remove explicit get_internals() from TEST_CASE("Threads") and REQUIRE(has_pybind11_internals_static()); along with it, based on #4218 (comment)

Author: rwgk

tests/test_embed/test_interpreter.cpp

@@ -292,11 +292,6 @@ TEST_CASE("Threads") {
     auto locals = py::dict("count"_a = 0);
 
     {
-        // This used to be triggered by py::gil_scoped_release().
-        // TODO: Explain why/how this is relevant to this unit test.
-        py::detail::get_internals();
-        REQUIRE(has_pybind11_internals_static());
-
         py::gil_scoped_release gil_release{};
 
         auto threads = std::vector<std::thread>();