It should be set by default. The pin, when used as digital, has the schmitt trigger as input. The output is however open-drain (i.e. it needs a pull-up if you want to use it).

From the datasheet:

"Pin RA4 is multiplexed with the Timer0 module clock
input to become the RA4/T0CKI pin. The RA4/T0CKI
pin is a Schmitt Trigger input and an open-drain output."

The pin is also shared as a comparator output, but by default it is off:

"On a Power-on Reset, these pins are configured as analog inputs and read as ‘0’. The comparators are in the off (digital) state."

Hope it helps.