devel/py-azure-synapse-artifacts: Update to 0.21.0

• Update WWW
• Convert to USE_PYTHON=pep517
• Update pkg-descr

Changes: https://github.com/Azure/azure-sdk-for-python/releases

		https://github.com/Azure/azure-sdk-for-python/blob/main/sdk/synapse/azure-synapse-artifacts/CHANGELOG.md