tests: monkeypatch secondary reference to gguf_sd_loader()

`gguf_sd_loader()` has multiple references in the codebase. It is imported before monkeypatching, so we need to monkeypatch another reference to it. This fixes tests for `ModelOnDisk.load_state_dict()`.

Author: psychedelicious

tests/conftest.py

@@ -94,6 +94,7 @@ def override_model_loading(monkeypatch):
     monkeypatch.setattr(safetensors.torch, "load", load_stripped_model)
     monkeypatch.setattr(safetensors.torch, "load_file", load_stripped_model)
     monkeypatch.setattr(gguf_loaders, "gguf_sd_loader", load_stripped_model)
+    monkeypatch.setattr("invokeai.backend.model_manager.config.gguf_sd_loader", load_stripped_model)
 
     def fake_scan(*args, **kwargs):
         return SimpleNamespace(infected_files=0, scan_err=None)