Dashboard pages try to load all activity

[benhaynes]

From directus created by bensteers : directus/directus#2177

When you go to a dashboard edit page, e.g. /tables/[table]/1, it tries to load all of the revisions into the right sidebar. But when I was dealing with #2176, our directus_activity table got to ~7 million records, so the pages just wouldn't load and they would hang on the Loading Data message. It wasn't until I dumped the directus_activity rows that I was able to use those pages again. I'd recommend limiting that query to something like ~100 revisions, just so that even if the directus_activity does explode, the app is still usable.