fix doc string (#5)

src/anemoi/models/layers/conv.py

@@ -77,7 +77,7 @@ def aggregate(self, edges_new: Tensor, edge_index: Adj, dim_size: Optional[int]
 
 class GraphTransformerConv(MessagePassing):
     """Message passing part of graph transformer operator.
-    
+
     Adapted from 'Masked Label Prediction: Unified Message Passing Model for Semi-Supervised Classification'
     (https://arxiv.org/abs/2009.03509)
     """