c-ares: bump to 1.34.8

c-ares: bump to 1.34.8

Update c-ares from 1.34.6 to 1.34.8.

Version 1.34.7 includes the following security fixes:

* CVE-2026-33630 (GHSA-6wfj-rwm7-3542): fix a use-after-free /
  double-free issue in query-completion handling.
* CVE-2026-69184 (GHSA-pjmc-gx33-gc76): limit DNS name compression
  pointer traversal to prevent CPU-exhaustion denial of service.
* CVE-2026-69186 (GHSA-jv8r-gqr9-68wj): validate DNS record counts
  before allocation to prevent memory-amplification denial of service.

It also fixes the UDP socket exhaustion regression introduced in 1.34.6.

Version 1.34.8 reverts an unintended API break introduced in 1.34.7 by
the callback parameter const changes.

Signed-off-by: Karen Khachatryan <redacted>