Fix Flatpak-from-RPM build
    
    ...after flatpak-rpm-macros-31-1 now causes the runtime dependency flute to
    (correctly) install flute.jar in /app/share/java/ rather than /usr/share/java/.
    
    (Technically, passing a correct --with-flute-jar=... is not strictly necessary
    prior to upstream <https://gerrit.libreoffice.org/c/core/+/91039> "Fix test for
    /usr/share/java/flute-1.3.0.jar", but better fix it anyway.)