Error: set log_error_verbosity to verbose fails

Looks like a minor oversight.

rbt=# set log_error_verbosity to terse;
SET
rbt=# set log_error_verbosity to default;
SET
rbt=# set log_error_verbosity to verbose;
ERROR:  syntax error at or near "verbose" at character 28
LINE 1: set log_error_verbosity to verbose;                                  ^
rbt=# set log_error_verbosity to 'terse';
SET
rbt=# set log_error_verbosity to 'verbose';
SET
rbt=# set log_error_verbosity to 'verboset';
ERROR:  invalid value for parameter "log_error_verbosity": "verboset"