GIT_SILENT: use PIM_VERSION variable everywhere

CMakeLists.txt

-set(KDEPIM_VERSION_NUMBER "5.14.40")
+set(PIM_VERSION "5.14.40")
 cmake_minimum_required(VERSION 3.5)
-project(mbox-importer VERSION ${KDEPIM_VERSION_NUMBER})
+project(mbox-importer VERSION ${PIM_VERSION})
 
 set(KF5_MIN_VERSION "5.68.0")
 
@@ -34,11 +34,11 @@ if(DEFINED KDEPIM_DEV_VERSION)
     set(KDEPIM_DEV_VERSION " ${KDEPIM_DEV_VERSION}")
 endif()
 
-set(KDEPIM_VERSION "${KDEPIM_VERSION_NUMBER}${KDEPIM_DEV_VERSION} (${RELEASE_SERVICE_VERSION})")
+set(KDEPIM_VERSION "${PIM_VERSION}${KDEPIM_DEV_VERSION} (${RELEASE_SERVICE_VERSION})")
 
 set(AKONADI_VERSION "5.14.40")
 
-set(KDEPIM_LIB_VERSION "${KDEPIM_VERSION_NUMBER}")
+set(KDEPIM_LIB_VERSION "${PIM_VERSION}")
 set(KDEPIM_LIB_SOVERSION "5")
 
 set(QT_REQUIRED_VERSION "5.12.0")