Remove too strict KF5 deprecation rule

GIT_SILENT

(cherry picked from commit 5dae82b6)

CMakeLists.txt

@@ -47,9 +47,7 @@ option(BUILD_GSTREAMER_PLUGIN "Build GStreamer sound backend" OFF)
 add_definitions(
     -DQT_NO_URL_CAST_FROM_STRING
 )
-if (EXISTS "${CMAKE_SOURCE_DIR}/.git")
-   add_definitions(-DKF_DISABLE_DEPRECATED_BEFORE_AND_AT=0x060000)
-endif()
+
 # subdirectories to build
 ecm_optional_add_subdirectory(data)
 ecm_optional_add_subdirectory(doc)