Update tests/test_additional_headers_simple.py

Co-authored-by: greptile-apps[bot] <165735046+greptile-apps[bot]@users.noreply.github.com>

Author: hassiebp

tests/test_additional_headers_simple.py

@@ -157,7 +157,7 @@ def test_span_processor_has_additional_headers_in_otel_exporter(self):
         # Verify default headers are still present
         assert "Authorization" in exporter._headers
         assert "x-langfuse-sdk-name" in exporter._headers
-        assert "x_langfuse_public_key" in exporter._headers
+        assert "x-langfuse-public-key" in exporter._headers
 
         # Check that our override worked
         assert exporter._headers["X-Override-Default"] == "override-value"