docs: update docs for the afcl datepicker

https://web.tracklify.com/project/2b7ZVgE5/AdminForth/1248/GHNwRaoK/afcl-datepicker-doesn't-work

Author: yaroslav8765

adminforth/documentation/docs/tutorial/03-Customization/15-afcl.md

@@ -2215,7 +2215,7 @@ const datePickerValue = ref()
 <div>
 ```html
 <DatePicker
-  v-model:datePickerValue="datePickerValue"
+  v-model:valueStart="datePickerValue"
   :column="{ type: 'datetime' }"
   label="Pick start"
 />