fix: allow creating Shift Assignment for same day (#28613) (#28630)

(cherry picked from commit 4458b24813)

Co-authored-by: Rucha Mahabal <ruchamahabal2@gmail.com>

erpnext/hr/doctype/shift_assignment/shift_assignment.py

@@ -19,8 +19,8 @@ class ShiftAssignment(Document):
 		validate_active_employee(self.employee)
 		self.validate_overlapping_dates()
 
-		if self.end_date and self.end_date <= self.start_date:
-			frappe.throw(_("End Date must not be lesser than Start Date"))
+		if self.end_date:
+			self.validate_from_to_dates('start_date', 'end_date')
 
 	def validate_overlapping_dates(self):
 		if not self.name: