misc/qt5ct: update to 1.7

Version 1.6

• added XDG desktop portal dialogs support (Marco Genasci)
• added qt6ct compatibility
• improved warning about incorrect environment variable
• improved icon loader
• only prepend our stylesheet if it has changed (Carlo Teubner)
• changed minimal required Qt version from 5.4 to 5.9
• fixed compatibility with applications that use own stylesheet (John Lindgren)
• fixed some clazy and clang-tidy warnings
• changed font configuration format
• updated Bulgarian translation (Kiril Kirilov)
• updated Catalan translation (Toni Estévez)
• updated Chinese (Traditional) translation (s8321414)
• updated Czech translation (fri)
• updated Dutch translation (Heimen Stoffels)
• updated Greek translation (Dimitrios Glentadakis)
• updated Japanese translation (UTUMI Hirosi)
• updated Polish translation (Marek Adamski)
• updated Russian translation (Ilya Kotov)
• updated Spanish translation (Toni Estévez)
• updated Ukrainian translation (Denys Nykula)

Version 1.7

• added keywords entry to desktop file (Mateusz Łukasik)
• changed minimal Qt version to 5.15 for cmake build system
• fixed qmake build