Silence clang-tidy for the hidden type_name() in the base class test

ci_clang_tidy failed with readability-convert-member-functions-to-static
on base_class_with_hidden_members::type_name(). It must stay a
non-static member: the test shows that it is hidden by the non-static
basic_json::type_name() and reachable through as_base_class().

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

tests/src/unit-custom-base-class.cpp

@@ -340,7 +340,7 @@ TEST_CASE("JSON Visit Node")
 class base_class_with_hidden_members
 {
   public:
-    const char* type_name() const noexcept
+    const char* type_name() const noexcept // NOLINT(readability-convert-member-functions-to-static)
     {
         return "custom type_name";
     }