[no ci] remove unnecessary serializable decorator on rmse

Author: vpratz

bayesflow/metrics/functional/root_mean_squared_error.py

@@ -2,10 +2,8 @@
 from keras import ops
 
 from bayesflow.types import Tensor
-from bayesflow.utils.serialization import serializable
 
 
-@serializable("bayesflow.metrics")
 def root_mean_squared_error(x1: Tensor, x2: Tensor, normalize: bool = False, **kwargs) -> Tensor:
     """Computes the (normalized) root mean squared error between samples x1 and x2.