python-urllib3: update to 2.6.3

python-urllib3: update to 2.6.3

- Fixed HTTPResponse.read_chunked() to properly handle leftover data
  in the decoder's buffer when reading compressed chunked responses.
- Fixed a security issue where decompression-bomb safeguards of the
  streaming API were bypassed when HTTP redirects were followed.
  (CVE-2026-21441)
- Started treating Retry-After times greater than 6 hours as 6 hours
  by default.
- Fixed urllib3.connection.VerifiedHTTPSConnection on Emscripten.

Release notes:
https://github.com/urllib3/urllib3/releases/tag/2.6.2
https://github.com/urllib3/urllib3/releases/tag/2.6.3

Signed-off-by: Wei-Ting Yang <williamatcg@gmail.com>