ruff: Fix C416 Unnecessary `set` comprehension (rewrite using `set()`).
ruff: Fix C416 Unnecessary `set` comprehension (rewrite using `set()`).

Signed-off-by: Anders Kaseorg <dfdb7392591db597bc41cf266a9c3bc12a2706e5@zulip.com>

zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip