ref(crons): Remove unused non-org endpoints

[evanpurkhiser]

1. The monitor details and monitor stats endpoint had additional org-less routes that were legacy from when this feature was first built.

2. The attachments endpoint was just named wrong

I've verified these endpoints are not being used with the following query

SELECT
  COUNT(*),
  jsonPayload.path
FROM
  `internal-sentry.getsentry_api_access_logs.stderr`
WHERE
  DATE(timestamp) = "2023-02-01"
  AND jsonPayload.view IN ('sentry.api.endpoints.monitor_stats.MonitorStatsEndpoint', 'sentry.api.endpoints.monitor_details.MonitorDetailsEndpoint')
  and NOT CONTAINS_SUBSTR(jsonPayload.path, 'organization')
GROUP BY
  2
ORDER BY
  1 desc

which returns no results

This is in support of #45166