Update dependency undici to ^6.21.0

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
undici (source)	^6.20.1 -> ^6.21.0

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Release Notes

nodejs/undici (undici)

v6.21.0

Compare Source

What's Changed

• [Backport v6.x] web: mark as uncloneable when possible (#​3709) by @​jazelly in https://github.com/nodejs/undici/pull/3744
• [Backport v6.x] fetch: fix content-encoding order by @​github-actions in https://github.com/nodejs/undici/pull/3764
• [Backport v6.x] fix: handle undefined deref() of WeakRef(socket) by @​github-actions in https://github.com/nodejs/undici/pull/3822
• [Backport v6.x] fix: range end is zero-indexed by @​github-actions in https://github.com/nodejs/undici/pull/3827

Full Changelog: nodejs/undici@v6.20.1...v6.21.0

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