Making safetensors a core dependency. (#23254)

* Making `safetensors` a core dependency.

To be merged later, I'm creating the PR so we can try it out.

* Update setup.py

* Remove duplicates.

* Even more redundant.

setup.py

@@ -321,7 +321,6 @@ extras["testing"] = (
         "protobuf",  # Can be removed once we can unpin protobuf
         "sacremoses",
         "rjieba",
-        "safetensors",
         "beautifulsoup4",
     )
     + extras["retrieval"]
@@ -425,6 +424,7 @@ install_requires = [
     deps["regex"],  # for OpenAI GPT
     deps["requests"],  # for downloading models over HTTPS
     deps["tokenizers"],
+    deps["safetensors"],
     deps["tqdm"],  # progress bars in model download and training scripts
 ]