Remove the uninitialized field "embedding" in nn.Embed

The presence of this field breaks dataclasses.asdict() but it doesn't seem to serve much purpose. It was added in a change that tries to reduce gpylint errors but removing this line does not trigger any new gpylint error.

PiperOrigin-RevId: 620422049

flax/linen/linear.py

@@ -14,7 +14,6 @@
 
 """Linear modules."""
 
-import dataclasses
 from typing import (
   Any,
   Iterable,
@@ -1105,8 +1104,6 @@ class Embed(Module):
   param_dtype: Dtype = jnp.float32
   embedding_init: Initializer = default_embed_init
 
-  embedding: Array = dataclasses.field(init=False)
-
   def setup(self):
     self.embedding = self.param(
       'embedding',