I believe Ryan is correct in that a soft start (SS) capacitor is not required. Evidence of this would include the following information from the datasheet:
Note that both in the specification table on page 3 and the graph, Fig.67 on page 19, show characteristics for the regulator under zero SS capacitance conditions.
I believe the internal circuit is a little more complex than what you have drawn. Just above the Fig. 67 graph on page 19, it gives the formula for soft start time as:
Note that Vref is 1.22V rather than the 5mV you came up with above. This implies that the resistor you drew is not connected to the circuit when Enable is high. I believe there is a separate switch between the 5k resistor and the SS cap which is only closed when Enable is low, and its only purpose is to quickly discharge the SS cap.
In conclusion, the soft start capacitor is not required for proper functionality of the regulator, and is only necessary if you wish to limit the inrush current of the regulator and/or control the rise time of the output voltage.