typo in parallel safety doc

Justin Pryzby <pryzby@telsasoft.com>

From: Justin Pryzby <pryzby@telsasoft.com>
To: pgsql-docs@postgresql.org
Date: 2018-08-16T19:54:31Z
Lists: pgsql-docs
https://www.postgresql.org/docs/10/static/parallel-safety.html
|Even for simple functions where it conceivably be done, we do not try, since this would be expensive and error-prone.

should say:
"where it COULD conceivably"


Commits

  1. Proof-reading for documentation.