Remove unused constant to fix macOS build warning

MAX_QUANTIZATION_REFERENCE_ERROR was defined but never used, causing
-Werror,-Wunused-const-variable build failure on macOS.

Co-Authored-By: Alex Peng <[email protected]>

Author: devin-ai-integration[bot]

tests/test-conversion-accuracy.cpp

@@ -19,7 +19,6 @@
 #pragma warning(disable: 4244 4267) // possible loss of data
 #endif
 
-constexpr float MAX_QUANTIZATION_REFERENCE_ERROR = 0.0001f;
 constexpr float MAX_QUANTIZATION_TOTAL_ERROR = 0.002f;
 constexpr float MAX_QUANTIZATION_TOTAL_ERROR_TERNARY = 0.01f;
 constexpr float MAX_QUANTIZATION_TOTAL_ERROR_2BITS = 0.0075f;