add reshape to fix use_memory_efficient_attention in flax

Author: jfacevedo-google

src/diffusers/models/attention_flax.py

@@ -216,8 +216,8 @@ def __call__(self, hidden_states, context=None, deterministic=True):
             hidden_states = jax_memory_efficient_attention(
                 query_states, key_states, value_states, query_chunk_size=query_chunk_size, key_chunk_size=4096 * 4
             )
-
             hidden_states = hidden_states.transpose(1, 0, 2)
+            hidden_states = self.reshape_batch_dim_to_heads(hidden_states)
         else:
             # compute attentions
             if self.split_head_dim: