[LoRA] Make optional arguments explicit (#5038)

make optional arguments explciit

src/diffusers/models/transformer_2d.py

@@ -284,7 +284,7 @@ def forward(
 
             hidden_states = self.norm(hidden_states)
             if not self.use_linear_projection:
-                hidden_states = self.proj_in(hidden_states, lora_scale)
+                hidden_states = self.proj_in(hidden_states, scale=lora_scale)
                 inner_dim = hidden_states.shape[1]
                 hidden_states = hidden_states.permute(0, 2, 3, 1).reshape(batch, height * width, inner_dim)
             else: