ci: Update dependency cloudflare/quiche to v0.21.0

[renovate]

This PR contains the following updates:

Package	Update	Change
cloudflare/quiche	minor	0.20.0 -> 0.21.0

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Release Notes

cloudflare/quiche (cloudflare/quiche)

v0.21.0: 🛰️ 0.21.0

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Highlights:

• Added initial implementation of path MTU discovery. Note that this feature is experimental and might have bugs.
• Added support to build against the "quictls" OpenSSL fork. Note that some features (e.g. 0-RTT) do not work yet in this mode.
• Many more bug fixes and performance improvements.

Full changelog at cloudflare/quiche@0.20.0...0.21.0

v0.20.1: 🔒 0.20.1

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⚠️ Security:

• Added a limit to how many connection IDs are locally queued for retirement. Without the limit an attacker could cause a server to queue an unbounded number of retired connection IDs, leading to a slow but steady increase in memory usage (CVE-2024-1410).
• Added a limit to the maximum CRYPTO frame data offset that can be buffered. Without the limit an attacker could cause a server to queue an unbounded number of bytes, leading to a slow but steady increase in memory usage (CVE-2024-1765).

Full changelog at cloudflare/quiche@0.20.0...0.20.1

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Configuration

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