Provide palettes as functions

Change-Id: Idc93e5c4538233ceaf248530e98a20cdcac38764
diff --git a/R/highcharter-themes.R b/R/highcharter-themes.R
index 9030d90..f934f43 100644
--- a/R/highcharter-themes.R
+++ b/R/highcharter-themes.R
@@ -44,7 +44,7 @@
            textColor = textColorDark,
            lowContrastColor = lowContrastColorDark,
            highContrastColor = highContrastColorDark,
-           palette = idsPalette,
+           palette = idsPalette(),
            backgroundColor = list(linearGradient = list(
              x1 = 0,
              y1 = 1,