Use bitsandbytes 0.40.0.post4 with bias hotfix (#342)

This PR includes a bnb hotfix: https://github.com/TimDettmers/bitsandbytes/commit/90b0ac57b0d8d8f996126deb8bba6b7dc75b4327

setup.cfg

@@ -32,7 +32,7 @@ packages = find:
 python_requires = >=3.7
 install_requires =
     torch>=1.12
-    bitsandbytes==0.40.0.post3
+    bitsandbytes==0.40.0.post4
     accelerate>=0.16.0,<1.0.0
     huggingface-hub>=0.11.1,<1.0.0
     tokenizers>=0.13.3