going back to older date format

Author: bast

content/plotting-vega-altair/data/README.md

@@ -6,5 +6,3 @@ The following changes were applied to the data to make it easier to work with:
 - The decimal separator was changed from a comma to a period.
 - The column separator was changed from a semicolon to a comma.
 - Missing values were replaced with zeros instead of a dash.
-- The date format was changed from DD.MM.YYYY and MM.YYYY to YYYY-MM-DD and
-  YYYY-MM.