Update Logs docs to state logger's log level is respected

[szokeasaurusrex]

When Sentry Logs are created via the Sentry SDKs logging integration, the logger's level is respected. However, our logs docs don't make this clear, causing confusion.

I discovered this while investigating getsentry/sentry-python#4415; we should add this information to the docs so future user's don't get confused by this behavior (and to make it easier for us to debug if we get similar reports from users in the future)