Geo: Add more warnings to the Remove Geo node confirmation modal

For an installation that is in use, removing a Geo node has more serious consequences than "stops the sync process". It sounds like it pauses it.

• The event log will quickly become stale (and also deleted), requiring a resync/recheck of everything on affected secondaries to guarantee complete sync.

I'm not sure what else would happen. We should test:

• Removing and readding a primary Geo node in UI
  • Are there any errors in UI?
  • Are there any errors in the Rails or geo logs?
• Removing and readding a secondary Geo node in UI
  • Are there any errors in UI?
  • Are there any errors in the Rails or geo logs?

/cc @akaemmerle @rnienaber