build(deps): Bump boto3 from 1.19.11 to 1.20.3

Bumps [boto3](https://github.com/boto/boto3) from 1.19.11 to 1.20.3.
- [Release notes](https://github.com/boto/boto3/releases)
- [Changelog](https://github.com/boto/boto3/blob/develop/CHANGELOG.rst)
- [Commits](boto/boto3@1.19.11...1.20.3)

---
updated-dependencies:
- dependency-name: boto3
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

requirements/base.txt

@@ -53,7 +53,7 @@ django-import-export==2.6.1
 gitpython==3.1.24
 
 # S3 Uploads
-boto3==1.19.11
+boto3==1.20.3
 django-storages==1.12.3  # https://github.com/jschneier/django-storages
 
 # Python function to stream unzip all the files in a ZIP archive, without loading the entire ZIP file into memory or any of its uncompressed files.