Avoid use of sprintf/snprintf in describe.c.
Most places were already using the PQExpBuffer library for constructing
variable-length strings; bring the two stragglers into line.
describeOneTSParser was living particularly dangerously since it wasn't
even using snprintf().
Daniel Gustafsson
Discussion: https://postgr.es/m/
3641F19B-336A-431A-86CE-
A80562505C5E@yesql.se