Update model arg name rope_theta to be consistent with those in llama's website

As title

Author: iseeyuan

examples/models/llama2/llama_transformer.py

@@ -88,7 +88,7 @@ class ModelArgs:
     use_sdpa_with_kv_cache_op: bool = (
         False  # Use custom sdpa op that updates kv cache in-place
     )
-    rope_freq_base: float = 10000.0  # The base frequency for RoPE
+    rope_theta: float = 10000.0  # The base frequency for RoPE
     # Additional Model Metadata needed at runtime
     bos_idx: int = 1
     eos_idx: int = 3
@@ -448,7 +448,7 @@ def __init__(self, params: ModelArgs):
                 if params.ffn_dim_multiplier is None
                 else params.max_seq_len * 2  # Sharded checkpoint.
             ),
-            params.rope_freq_base,
+            params.rope_theta,
         )
         self.register_buffer("freqs_cos", freqs_cos, persistent=False)
         self.register_buffer("freqs_sin", freqs_sin, persistent=False)