Add int4 config for starcoder2-15b (#1285)

* int4 config for starcoder2-15b

* Update configuration.py

Author: MaximProshin

optimum/intel/openvino/configuration.py

@@ -196,6 +196,7 @@ class OVQuantizationMethod(str, Enum):
         "scale_estimation": True,
     },
     "bigcode/starcoder2-3b": {"bits": 4, "sym": False, "group_size": 128, "ratio": 0.9},
+    "bigcode/starcoder2-15b": {"bits": 4, "sym": False, "group_size": 64, "ratio": 1.0},
     "TinyLlama/TinyLlama-1.1B-Chat-v1.0": {
         "bits": 4,
         "sym": False,