Drop pre Qt5.12 workarounds

Test Plan: None

Reviewers: #plasma, #kwin, zzag

Reviewed By: #plasma, #kwin, zzag

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D18514

CMakeLists.txt

@@ -4,7 +4,7 @@ project(plasma-workspace)
 set(PROJECT_VERSION "5.15.80")
 set(PROJECT_VERSION_MAJOR 5)
 
-set(QT_MIN_VERSION "5.11.0")
+set(QT_MIN_VERSION "5.12.0")
 set(KF5_MIN_VERSION "5.54.0")
 set(INSTALL_SDDM_THEME TRUE)
 find_package(Qt5 ${QT_MIN_VERSION} CONFIG REQUIRED COMPONENTS Widgets Quick QuickWidgets Concurrent Test Network)

logout-greeter/main.cpp

@@ -34,10 +34,6 @@ CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 int main(int argc, char *argv[])
 {
-    if (QLibraryInfo::version() < QVersionNumber(5, 12)) {
-        // Before Qt 5.12, the xdg-shell v6 integration does not support fullscreen.
-        qputenv("QT_WAYLAND_SHELL_INTEGRATION", "wl-shell");
-    }
     qunsetenv("SESSION_MANAGER");
 
     KWorkSpace::detectPlatform(argc, argv);