update create-score-version github action to upload files to S3 for beta version only

[vim-usds]

Describe the bug

1. In the create-score-version github action, line 85, is currently copying contents from the files directory to downloadable folder on S3. This is happening on all builds. This should only happen when the target version is beta.
2. There are some curl commands that check the existence of downloadable files, which may not be needed any more.

To Reproduce Steps to reproduce the behavior:

1. When create-score-version is run, it will write the contents of files to the S3 downloadable folder

Expected behavior The expected behavior is for this to only occur when the target version is beta.

Ideally, we may want to create a specific folder for the beta files. This would allow for other versions in the future.