doc: Fix syntax in ALTER FOREIGN DATA WRAPPER example
The example for dropping an option was incorrectly quoting the
option key thus making it a value turning the command into an
unqualified ADD operation. The result of dropping became adding
a new key/value pair instead:
d=# alter foreign data wrapper f options (drop 'b');
ALTER FOREIGN DATA WRAPPER
d=# select fdwoptions from pg_foreign_data_wrapper where fdwname='f';
fdwoptions
------------
{drop=b}
(1 row)
This has been incorrect for a long time so backpatch to all
supported branches.
Author: Tim <tim.needham2@gmail.com>
Discussion: https://postgr.es/m/
170292280173.
1876505.
5204623074024041738@wrigleys.postgresql.org