Release Notes 5.10.0 (#818)

This PR updates and reformats the Release Notes for the deployment
repos. Adding warnings about the v5.10.0 postgres version upgrades and
its impact on database upgrades, and reformating and cleaning up the old
version release notes.

## Pull Request approval

@Chickensoupwithrice

Author: DaedalusG

docs/admin/updates/automatic.mdx

@@ -1,5 +1,7 @@
 # Automatic multi-version upgrades
 
+> Warning: Automatic upgrades in v5.10.0 will fail unless the postgres database is upgraded from postgres 12 to postgres 16. Or the environment variable `SRC_AUTOUPGRADE_IGNORE_DRIFT=true` is set on the `sourcegraph-frontend` container. 
+
 From **Sourcegraph 5.1 and later**, multi-version upgrades can be performed **automatically** as if they were a standard upgrade for the same deployment type. Automatic multi-version upgrades take the following general form:
 
 1. Determine if your instance is ready to Upgrade: