Pass Size as a 2nd argument for snprintf() in tablesync.c.

Pass Size as a 2nd argument for snprintf() in tablesync.c.

Previously the following snprintf() wrappers:

* ReplicationSlotNameForTablesync()
* ReplicationOriginNameForTablesync()

... used int as a second argument of snprintf() while the actual type of it
is size_t. Although it doesn't fail at present better replace it with Size
for consistency with the rest of the system.

Author: Aleksander Alekseev
Reviewed-By: Peter Smith
Discussion: https://postgr.es/m/CAHut%2BPsa8hhfSE6ozUK-ih7GkQziAVAf4f3bqiXEj2nQiu-43g%40mail.gmail.com