Stop after first EOS post-promptfor FS2 (#2255)

Summary:

Stop after first EOS post-promptfor FS2

Reviewed By: shoumikhin

Differential Revision: D54525365

Author: Michael Gschwind

examples/models/llama2/builder.py

@@ -231,7 +231,7 @@ def _get_metadata(self):
             "get_max_batch_size": params.max_batch_size,
             "get_max_seq_len": params.max_seq_len,
             "get_n_bos": 1,
-            "get_n_eos": 2 if is_fairseq2 else 1,
+            "get_n_eos": 1,  # 2 if is_fairseq2 else 1,
             "get_n_kv_heads": params.n_kv_heads,
             "get_n_layers": params.n_layers,
             "get_vocab_size": params.vocab_size,