[HIGH] Bump undici to 7.29.1

[OskarEichler]

Summary

• update @electron/get’s undici 7.x lockfile entry from 7.25.0 to 7.29.1
• leave the unaffected React Native dev-middleware 6.x line unchanged
• remain within the existing compatible 7.x range

Security impact

undici 7.25.0 is affected by multiple advisories fixed in 7.28.0/7.29.0, including cross-user cache disclosure, SOCKS5 cross-origin routing and TLS validation bypass, WebSocket denial of service, response desynchronization, and header/cookie injection (GHSA-4cwx-7wf7-3272, GHSA-hm92-r4w5-c3mj, GHSA-vmh5-mc38-953g, GHSA-vxpw-j846-p89q, GHSA-8xcm-r25x-g524, GHSA-m8rv-5g2x-5cg5, and related 7.x advisories).

Test Plan

• yarn install --frozen-lockfile --ignore-scripts
• yarn why undici confirmed the affected line at 7.29.1
• yarn audit no longer reports undici advisories
• yarn build
• debugger-shell: 4 suites, 9 tests, 4 snapshots passed
• Jest retained a pre-existing open handle after reporting success and was stopped after completion
• git diff --check

Changelog:

[INTERNAL] [SECURITY] - Bump undici to 7.29.1.