Only enable R4 as default setting

Random R1 and R2 matrices are showing better results than just using R4, so the latter seems to be a better default option (at least for now)

torchao/prototype/spinquant/spinquant.py

@@ -32,7 +32,7 @@ def forward(self, x):
         return x
 
 
-def apply_spinquant(model: Transformer, use_r1=False, use_r2=True, use_r4=True, pretrained_rotation_path=None):
+def apply_spinquant(model: Transformer, use_r1=False, use_r2=False, use_r4=True, pretrained_rotation_path=None):
     """
     Apply SpinQuant to a Transformer model: https://arxiv.org/abs/2405.16406