Fix docker build issue caused by missing dependency of tomli

[sarutak]

Description

docker build for build.ubuntu-1804-sgx-2.17.1.Dockerfile and build.ubuntu-1804-sgx-dcap-1.14.Dockerfile fails due to missing dependency of tomli, a Python library.

$ docker build -t ubuntu-1804-sgx-2.17.1:latest . -f  docker/build.ubuntu-1804-sgx-dcap-1.14.Dockerfile
  Could not find a version that satisfies the requirement tomli>=2.0.1 (from yapf) (from versions: 0.2.0, 0.2.1, 0.2.2, 0.2.3, 0.2.4, 0.2.5, 0.2.6, 0.2.7, 0.2.8, 0.2.9, 0.2.10, 1.0.0, 1.0.1, 1.0.2, 1.0.3, 1.0.4, 1.1.0, 1.2.0, 1.2.1, 1.2.2, 1.2.3)
No matching distribution found for tomli>=2.0.1 (from yapf)
The command '/bin/sh -c pip3 install pyopenssl==21.0.0 toml cryptography yapf requests Pillow' returned a non-zero code: 1

I confirmed this issue doesn't happen with build.ubuntu-2004-sgx-2.17.1.Dockerfile or build.ubuntu-2004-sgx-dcap-1.14.Dockerfile.

Type of change (select or add applied and delete the others)

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] API change with a documentation update
• [ ] Additional test coverage
• [ ] Code cleanup or just sync with upstream third-party crates

How has this been tested?

Checklist

• [x] Fork the repo and create your branch from master.
• [x] If you've added code that should be tested, add tests.
• [x] If you've changed APIs, update the documentation.
• [x] Ensure the tests pass (see CI results).
• [x] Make sure your code lints/format.