Remove stub

Author: jackzhxng

extension/llm/tokenizer/hf_tokenizer.cpp

@@ -96,20 +96,3 @@ def define_common_targets():
             "re2",
         ],
     )
-
-    runtime.cxx_library(
-        name = "hf_tokenizer",
-        srcs = [
-            "hf_tokenizer.cpp",
-        ],
-        exported_headers = [
-            "hf_tokenizer.h",
-        ],
-        exported_deps = [
-            ":tokenizer_header",
-            "//executorch/runtime/core:core",
-        ],
-        visibility = [
-            "@EXECUTORCH_CLIENTS",
-        ],
-    )