Update config.json

Use the correct activation function : related discussion: https://huggingface.co/google/flan-t5-xxl/discussions/11

The previous config file was using gelu function instead of gated-gelu that is automatically set when forcing is_gated_actto True, more specifically here
This is not a breaking change since it fixes only for inference. Users that trained a model with gelu instead of gated-gelu should not be affected by this change.

config.json

@@ -6,13 +6,11 @@
   "d_kv": 64,
   "d_model": 4096,
   "decoder_start_token_id": 0,
-  "dense_act_fn": "gelu",
   "dropout_rate": 0.1,
   "eos_token_id": 1,
-  "feed_forward_proj": "gelu",
+  "feed_forward_proj": "gated-gelu",
   "initializer_factor": 1.0,
   "is_encoder_decoder": true,
-  "is_gated_act": true,
   "layer_norm_epsilon": 1e-06,
   "model_type": "t5",
   "num_decoder_layers": 24,