qt: Use 5.7 on Windows.

CMakeLists.txt

@@ -181,7 +181,7 @@ ENDIF (APPLE)
 if (ENABLE_QT)
     if (CITRA_USE_BUNDLED_QT)
         if (MSVC14 AND ARCHITECTURE_x86_64)
-            set(QT_VER qt-5.5-msvc2015_64)
+            set(QT_VER qt-5.7-msvc2015_64)
         else()
             message(FATAL_ERROR "No bundled Qt binaries for your toolchain. Disable CITRA_USE_BUNDLED_QT and provide your own.")
         endif()