shiny-demo: Use idsThemeR

Change-Id: Id2668f22dec411290711f9f863082627492b3ad2
diff --git a/demo/shiny-apps/frequency_curves/ui.R b/demo/shiny-apps/frequency_curves/ui.R
index f81b83f..2e1adee 100644
--- a/demo/shiny-apps/frequency_curves/ui.R
+++ b/demo/shiny-apps/frequency_curves/ui.R
@@ -3,7 +3,8 @@
 library(RKorAPClient)
 library(utils)
 library(stringr)
-source("theme-ids-dark.R")
+library(idsThemeR)
+#source("theme-ids-dark.R")
 
 shinyUI(
   fluidPage(