fix: forward extra_headers to HuggingFace embedding calls

Fixes #23502

The huggingface_embed.embedding() call was not receiving the headers
parameter, causing extra_headers (e.g., X-HF-Bill-To) to be silently
dropped. Other providers (openrouter, vercel_ai_gateway, bedrock) already
pass headers correctly. This fix adds headers=headers to match the
behavior of other providers.

litellm/main.py

@@ -5098,6 +5098,7 @@ def embedding(  # noqa: PLR0915
                 client=client,
                 aembedding=aembedding,
                 litellm_params=litellm_params_dict,
+                headers=headers,
             )
         elif custom_llm_provider == "bedrock":
             if isinstance(input, str):