Bump golang.org/x/net from 0.25.0 to 0.26.0

Bumps golang.org/x/net from 0.25.0 to 0.26.0.

Commits

• 66e838c go.mod: update golang.org/x dependencies
• 6249541 http2: avoid race in server handler SetReadDeadine/SetWriteDeadline
• 603e3e6 quic: disable X25519Kyber768Draft00 in tests
• 67e8d0c http2: report an error if goroutines outlive serverTester tests
• 5608279 http2: avoid corruption in priority write scheduler
• 0d515a5 http2: factor out frame read/write test functions
• 9f5b79b http2: drop unused retry function
• 03c24c2 http2: use synthetic time in server tests
• 022530c http2: add a more full-featured test net.Conn
• 410d19e http2: avoid racy access to clientStream.requestedGzip
• Additional commits viewable in compare view