fix(VDatePicker): round font-size from 13.6 to 14px (#21590)

Author: J-Sek

packages/vuetify/src/components/VDatePicker/_variables.scss

@@ -5,10 +5,10 @@ $date-picker-controls-height: var(--v-date-picker-controls-height, 56px) !defaul
 $date-picker-header-height: 70px !default;
 
 $date-picker-month-btn-height: 24px !default;
-$date-picker-month-btn-size: 0.85rem !default;
+$date-picker-month-btn-size: 0.875rem !default;
 $date-picker-month-column-gap: 4px !default;
 $date-picker-month-day-size: 40px !default;
-$date-picker-month-font-size: 0.85rem !default;
+$date-picker-month-font-size: 0.875rem !default;
 $date-picker-month-padding: 0 12px 8px !default;
 
 $date-picker-months-grid-gap: 0px 24px !default;