Remove second layer norm from phi component mapping (#1059)

* Remove second layer norm from phi component mapping

* Configure prepend_bos to be off by default

Author: degenfabian

transformer_lens/model_bridge/supported_architectures/phi.py

@@ -21,6 +21,8 @@
 class PhiArchitectureAdapter(ArchitectureAdapter):
     """Architecture adapter for Phi models."""
 
+    default_cfg = {"use_fast": False}
+
     def __init__(self, cfg: Any) -> None:
         """Initialize the Phi architecture adapter.
 
@@ -29,7 +31,7 @@ def __init__(self, cfg: Any) -> None:
         """
         super().__init__(cfg)
 
-        self.default_cfg = {"use_fast": False}
+        self.cfg.default_prepend_bos = False
 
         self.conversion_rules = HookConversionSet(
             {
@@ -96,8 +98,6 @@ def __init__(self, cfg: Any) -> None:
                             "o": LinearBridge(name="dense"),
                         },
                     ),
-                    # Layer norm 1 and 2 are tied.
-                    "ln2": NormalizationBridge(name="input_layernorm", config=self.cfg),
                     "mlp": MLPBridge(
                         name="mlp",
                         submodules={