fix README.md

Author: funbringer

README.md

@@ -104,8 +104,8 @@ It's quite easy to create a backup and start a new replica:
 with testgres.get_new_node('master') as master:
 master.init().start()
 with master.backup() as backup:
- replica = backup.spawn_replica('replica').start()
-print(replica.execute('postgres', 'select 1'))
+ replica = backup.spawn_replica('replica').start()
+print(replica.execute('postgres', 'select 1'))
 ```
 
 > Note: you could take a look at [`pg_pathman`](https://.com/postgrespro/pg_pathman) to get an idea of `testgres`' capabilities.