Reorder items in transaction.active_record docs

The `transaction.active_record` event is about transactions. Let's
first document the transaction object, then the transaction state,
and finally the connection in case you need more context.

Author: fxn

guides/source/active_support_instrumentation.md

@@ -412,9 +412,9 @@ This event is emmited for every transaction to the database.
 
 | Key                  | Value                                                |
 | -------------------- | ---------------------------------------------------- |
-| `:connection`        | Connection object                                    |
-| `:transaction`       | Transaction object
+| `:transaction`       | Transaction object                                   |
 | `:outcome`           | `:commit`, `:rollback`, `:restart`, or `:incomplete` |
+| `:connection`        | Connection object                                    |
 
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