fix default num_attention_heads in segformer doc (#16612)

src/transformers/models/segformer/configuration_segformer.py

@@ -54,7 +54,7 @@ class SegformerConfig(PretrainedConfig):
             Patch size before each encoder block.
         strides (`List[int]`, *optional*, defaults to [4, 2, 2, 2]):
             Stride before each encoder block.
-        num_attention_heads (`List[int]`, *optional*, defaults to [1, 2, 4, 8]):
+        num_attention_heads (`List[int]`, *optional*, defaults to [1, 2, 5, 8]):
             Number of attention heads for each attention layer in each block of the Transformer encoder.
         mlp_ratios (`List[int]`, *optional*, defaults to [4, 4, 4, 4]):
             Ratio of the size of the hidden layer compared to the size of the input layer of the Mix FFNs in the