FIX: flaky jobs_base_spec.rb (#8258)

I was searching for a reason for randomly failing jobs_base_spec.rb. The reason was that after restorer_spec, the database is not restored to default.
After restorer spec RailsMultisite::ConnectionManagement.all_dbs is returning array of ['default', 'second']

Then base job execution is evaluated twice
```
dbs = RailsMultisite::ConnectionManagement.all_dbs
dbs.each do |db|
     execute(opts)
end
```

spec/lib/backup_restore/restorer_spec.rb

@@ -110,6 +110,7 @@ describe BackupRestore::Restorer do
       described_class.any_instance.stubs(initialize_state: true)
     end
     after do
+      RailsMultisite::ConnectionManagement.clear_settings!
       conn.establish_connection(db: 'default')
     end
     let(:conn) { RailsMultisite::ConnectionManagement }