[partition] make the tests also build with Qt6

src/modules/partition/tests/CMakeLists.txt

@@ -3,12 +3,12 @@
 #   SPDX-FileCopyrightText: 2020 Adriaan de Groot <groot@kde.org>
 #   SPDX-License-Identifier: BSD-2-Clause
 #
-find_package(Qt5 COMPONENTS Gui REQUIRED)
+find_package(${qtname} COMPONENTS Gui REQUIRED)
 
 set(PartitionModule_SOURCE_DIR ..)
 
 include_directories(
-    ${Qt5Gui_INCLUDE_DIRS}
+    ${${qtname}Gui_INCLUDE_DIRS}
     ${PartitionModule_SOURCE_DIR}
     ${CMAKE_CURRENT_SOURCE_DIR}
     ${CMAKE_CURRENT_BINARY_DIR}