Update qt5 and kf5 version requirements

CMakeLists.txt

@@ -9,8 +9,8 @@ if("${CMAKE_SOURCE_DIR}" STREQUAL "${CMAKE_BINARY_DIR}")
    message(FATAL_ERROR "plasma requires an out of source build. Please create a separate build directory and run 'cmake path_to_plasma [options]' there.")
 endif()
 
-set(QT_MIN_VERSION 5.12.0)
-set(KF5_MIN_VERSION 5.72.0)
+set(QT_MIN_VERSION 5.15.0)
+set(KF5_MIN_VERSION 5.74.0)
 
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)