doc: fix a typo (#1850)

Author: Freed-Wu

bitsandbytes/nn/modules.py

@@ -434,7 +434,7 @@ class Linear4bit(nn.Linear):
     import torch.nn as nn
 
     import bitsandbytes as bnb
-    from bnb.nn import Linear4bit
+    from bitsandbytes.nn import Linear4bit
 
     fp16_model = nn.Sequential(
         nn.Linear(64, 64),
@@ -948,7 +948,7 @@ class Linear8bitLt(nn.Linear):
     import torch.nn as nn
 
     import bitsandbytes as bnb
-    from bnb.nn import Linear8bitLt
+    from bitsandbytes.nn import Linear8bitLt
 
     fp16_model = nn.Sequential(
         nn.Linear(64, 64),