Bug#1121193: dovecot-sieve: Regex extension ignored

[Noah Meyerhans]

Control: tags -1 + pending

> Ack. I neglected to add libpcre2-dev to build-deps for 2.4.2.  This will
> be corrected in the next upload.

Fixed with 
https://salsa.debian.org/debian/dovecot/-/commit/8d95d15e35567d285f73008a871afc6b6d7f45c1