appimage: Patch required cmake version (only if needed)

Requiring cmake version 3.26 for all packages caused a problem when
building kauth. To avoid other unexpected build problems only patch the
required cmake version if it's 3.27 (which the KDE PIM packages were
bumped to). In this case revert the required cmake version back to 3.16
(which was the previous required version of the KDE PIM packages).

• GnuPG-bug-id: T7509