mail/fetchmail: update to 6.4.28

BREAKING CHANGES:
* Bump wolfSSL minimum required version to 5.1.1 to pull in security fix.

FIXES:
* When using wolfSSL 5.0.0, work around a bug that appears to hit wolfSSL when
  receiving handshake records while still in SSL_peek(). Workaround is to read
  1 byte and cache it, then call SSL_peek() again.
  This affects only some servers. https://github.com/wolfSSL/wolfssl/issues/4593

TRANSLATIONS: language translations were updated by this fine people:
* es:    Cristian Othón Martínez Vera [Spanish]
* ro:    Remus-Gabriel Chelu [Romanian]
* sr:    Мирослав Николић (Miroslav Nikolić) [Serbian]

MFH:		2022Q1