Lower min KF5 Version for Windows

To develop for Windows we often compile libkleo and kleopatra
with older kde frameworks. The Gpg4win build system patched
that but it is better to have it in the repo itself.

The release scripts that bump the dependencies in general
should still work.
2 jobs for master
Status Job ID Name Coverage
canceled #76151

canceled #76150
linux kf5-qt5 qt5.12