Update docs: Use no_sign_request to fix "NoCredentials" Error when trying to access a public S3 bucket

[torrinworx]

I've outlined this issue in more depth here: https://stackoverflow.com/q/73708204/15739035

But essentially just using this simple code:

from cloudpathlib import CloudPath
path = r"C:\some\path\to\folder"
url = "s3://some-example-bucket/folder/"

cloud_path = CloudPath(url)
cloud_path.download_to(path)

I'm unable to download a folder from this S3 bucket: s3://cozy-auto-texture-sd-repo/stable-diffusion-v1-4/

Now this bucket needs to be public so I can distribute a repository to my users, and anyone needs to be able to access it. For some reason whenever I run the above code with that s3:// link, cloudpathlib gives the following error:

  File "E:\Cozy-Auto-Texture-Files\venv\lib\site-packages\botocore\auth.py", line 418, in add_auth
    raise NoCredentialsError()
botocore.exceptions.NoCredentialsError: Unable to locate credentials

[pjbull]

@torrinworx Like with boto3 directly, in order to access public resources anonymously you need to pass no_sign_request=True when you instantiate the S3Client (you can find examples here).

We'd take a PR that updates that authentication docs page to have an example accessing a public bucket so this is eaiser for other folks to find as well.