feat: copy update

config/locales/en.yml

@@ -331,7 +331,7 @@ en:
       type_of_unit: "Select the most common type of unit at this location"
       mobility_standards: "Select the mobility standard for the majority of the units at this location"
       startdate_blank: "Enter the day, month and year when the first property became available at this location"
-      startdate_invalid: "Enter a valid day, month and year when the first property became available at this location"
+      startdate_invalid: "Enter a valid day, month and year"
       toggle_date:
         not_selected: "Select one of the options"
         invalid: "Enter a valid day, month and year"