fix(uptime): Require span_id

[evanpurkhiser]

This is already always being set by the uptime checker. Correct the schema to match what we're doing

[github-actions[bot]]

versions in use:

The following repositories use one of the schemas you are editing. It is recommended to roll out schema changes in small PRs, meaning that if those used versions lag behind the latest, it is probably best to update those services before rolling out your change.

• getsentry/sentry: pip:sentry-kafka-schemas==0.1.106
• getsentry/uptime-checker: rust:sentry-kafka-schemas==0.1.103 (upgrade)

latest version: 0.1.106

changes considered breaking

**schemas/uptime-results.v1.schema.json** - ``` {"path": "", "change": {"RequiredAdd": {"property": "span_id"}}} ```

⚠️ This PR contains breaking changes. Normally you should avoid that and make your consumer backwards-compatible (meaning that updated consumers can still accept old messages). There are a few exceptions:

• If consumers already require these invariants in practice, and you're just adjusting the JSON schema to reality, ignore this warning.

• If you know what you are doing, this change could potentially be rolled out to producers first, but that's not a flow we support.