Cryptic CLI error in SageMaker Studio (and probably other role-based environments?)

Hi team,

I was surprised to find today that the below does not work in the default Python notebook kernel of a [SageMaker Studio JupyterLab space](https://docs.aws.amazon.com/sagemaker/latest/dg/studio-updated-jl.html), when the notebook's IAM execution role has all the necessary permissions:

```jupyter
%pip install amazon-textract-textractor

!textractor start-document-analysis \
--features LAYOUT --features TABLES \
--s3-upload-path {s3_upload_uri} \
--s3-output-path {s3_output_uri} \
data/my-cool-document.pdf
```

## Actual behaviour

When neither `--region-name` nor `--profile-name` are set, the CLI [auto-configures the profile](https://github.com/aws-samples/amazon-textract-textractor/blob/8cf3759adc4a9eee56f5ae1d15e778aa70bf88ca/textractor/cli/cli.py#L344) to "default", which causes the below error:

```
Traceback (most recent call last):
File "/opt/conda/bin/textractor", line 8, in
sys.exit(textractor_cli())
File "/opt/conda/lib/python3.10/site-packages/textractor/cli/cli.py", line 347, in textractor_cli
extractor = Textractor(
File "/opt/conda/lib/python3.10/site-packages/textractor/textractor.py", line 90, in __init__
self.session = boto3.session.Session(profile_name=self.profile_name)
File "/opt/conda/lib/python3.10/site-packages/boto3/session.py", line 90, in __init__
self._setup_loader()
File "/opt/conda/lib/python3.10/site-packages/boto3/session.py", line 131, in _setup_loader
self._loader = self._session.get_component('data_loader')
File "/opt/conda/lib/python3.10/site-packages/botocore/session.py", line 802, in get_component
return self._components.get_component(name)
File "/opt/conda/lib/python3.10/site-packages/botocore/session.py", line 1140, in get_component
self._components[name] = factory()
File "/opt/conda/lib/python3.10/site-packages/botocore/session.py", line 199, in
lambda: create_loader(self.get_config_variable('data_path')),
File "/opt/conda/lib/python3.10/site-packages/botocore/session.py", line 323, in get_config_variable
return self.get_component('config_store').get_config_variable(
File "/opt/conda/lib/python3.10/site-packages/botocore/configprovider.py", line 465, in get_config_variable
return provider.provide()
File "/opt/conda/lib/python3.10/site-packages/botocore/configprovider.py", line 671, in provide
value = provider.provide()
File "/opt/conda/lib/python3.10/site-packages/botocore/configprovider.py", line 761, in provide
scoped_config = self._session.get_scoped_config()
File "/opt/conda/lib/python3.10/site-packages/botocore/session.py", line 422, in get_scoped_config
raise ProfileNotFound(profile=profile_name)
botocore.exceptions.ProfileNotFound: The config profile (default) could not be found
```

## Expected behaviour

In this environment the `AWS_REGION` environment variable is automatically set, but there are no CLI 'profile's. I suggest a better default behaviour would be to auto-discover the region from environment variables when present (e.g. `os.environ.get("AWS_REGION")`) and leave the profile alone?