Update Oj to v3.13.21

Oj v3.13.16 introduced a new feature to obtain the line number and
column in the Simple API JSON (SAJ) parser
(https://github.com/ohler55/oj/pull/785), but there was a pointer type
error that caused a seg fault for certain inputs. The bug was fixed in
https://github.com/ohler55/oj/pull/809.

Diff: https://my.diffend.io/gems/oj/3.13.20/3.13.21

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/369046

Changelog: fixed