www/py-calibreweb: Update 0.6.26 => 0.6.27

This release contains bug and security fixes, also
updated to support www/py-flask-limiter v4 which in
turn removes the need for the port www/py-flask-limiter3.

Changes:
https://github.com/janeczku/calibre-web/releases/tag/0.6.27

PR: 297375
Reported by: Matthew Wener <matthew@wener.org> (maintainer)
Approved by: osa, vvd (Mentors, implicit)
Security: CVE-2025-6998
Security: CVE-2025-7404
MFH: 2026Q3

(cherry picked from commit 374c12ecb2f422cb6a7bee19689189c78e0097e4)