Simplify CMake rules for desktop file translations.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>

knights/CMakeLists.txt

@@ -49,5 +49,5 @@ tde_create_translated_desktop( ${PROJECT_NAME}.desktop )
 tde_create_translated_desktop(
     SOURCE pgn.desktop
     DESTINATION ${MIME_INSTALL_DIR}/application
-    PO_DIR ${CMAKE_SOURCE_DIR}/translations/desktop_files/pgn-mimetype
+    PO_DIR pgn-mimetype
 )