This grammar has no effect as there are no dependencies on statistics,
but it is supported by the parser.  This is more consistent with the
other DROP commands.

Author: Vignesh C
Discussion: https://postgr.es/m/CALDaNm1LA=yNmzcSfy+0oe6CEAgsxXRf_-UutE3ZncFi8QkFNQ@mail.gmail.com
Backpatch-through: 10