Update awscrt requirement from <=0.20.11,>=0.19.18 to <=0.21.0,>=0.21.0

[dependabot[bot]]

Updates the requirements on awscrt to permit the latest version.

Release notes

Sourced from awscrt's releases.

S3Client breaking change: DEFAULT requests must pass operation_name

What's Changed

• clang-format 18 by @​graebm in awslabs/aws-crt-python#571
• Always use virtual environments in CI, because PEP 668 by @​graebm in awslabs/aws-crt-python#573
• Fix editable build on Macs with XCode >= 15 by @​DmitriyMusatkin in awslabs/aws-crt-python#575
• S3Client breaking change: DEFAULT requests must pass operation_name by @​graebm in awslabs/aws-crt-python#574

Full Changelog: https://github.com/awslabs/aws-crt-python/compare/v0.20.12...v0.21.0

Commits

• 1424d91 S3Client breaking change: DEFAULT requests must pass operation_name (#574)
• 00a410f Fix editable build on Macs with XCode >= 15 (#575)
• 1d5103e Always use virtual environments in CI, because PEP 668 (#573)
• a486d70 clang-format 18 (#571)
• e88cce2 latest submodules (#570)
• c9c84bc Address issues with latest AWS-LC and OpenBSD (#569)
• 4a4fd22 fix docs.yml (#568)
• af29c15 Fix bug where last few bytes on socket go unread (#567)
• 23efdd7 Typing fixes (#566)
• 68afb70 Bind connack_timeout_ms for mqtt5 (#548)
• Additional commits viewable in compare view

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