pip(deps): update boto3 requirement from ~=1.20 to ~=1.21

Updates the requirements on [boto3](https://github.com/boto/boto3) to permit the latest version.
- [Release notes](https://github.com/boto/boto3/releases)
- [Changelog](https://github.com/boto/boto3/blob/develop/CHANGELOG.rst)
- [Commits](boto/boto3@1.20.0...1.21.3)

---
updated-dependencies:
- dependency-name: boto3
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

requirements/S3_REQUIREMENTS.txt

@@ -1,4 +1,4 @@
-boto3~=1.20
+boto3~=1.21
 botocore~=1.23
 hurry.filesize==0.9
 s3transfer~=0.5