Fix sobstitute offset calc in HolidayDefinition

Fix the calculation of the sobstitute offset for non-working days where DATETIME variable `_HolidayDateStep1` is used instead of the INT64 `_HolidayDayStep1`

src/Dax.Template/Tables/Dates/HolidaysTable.cs

@@ -274,7 +274,7 @@ NOT CONTAINS ( __WorkingDays, ''[Value], _HolidayDayStep1 ),
                             MINX ( __WorkingDays, ''[Value] ) + 7,
                             _NextWorkingDayStep2
                         )
-                    RETURN _SubstituteDay - _HolidayDateStep1
+                    RETURN _SubstituteDay - _HolidayDayStep1
                 )
             VAR _SubstituteOffsetStep2 = _SubstituteOffsetStep1 + _SubstituteHolidayOffsetNonWorkingDays
             VAR _SubstituteDateStep2 = _OriginalSubstituteDate + _SubstituteOffsetStep2