update default headdim to 128

Signed-off-by: h-guo18 <[email protected]>

Author: h-guo18

modelopt/torch/speculative/eagle/default_config.py

@@ -47,5 +47,5 @@
     "use_mtp_layernorm": False,
     "parallel_draft_step": 1,
     "has_lm_head": False,
-    "head_dim": 64,
+    "head_dim": 128,
 }