Small tweaks to sql.active_record guide

- reorder the keys to match the created payload (to make it easier to
  compare the two lists)
- add note that `statement_name` is Postgres only
- add missing `async` key to example payload

Author: skipkayhil

guides/source/active_support_instrumentation.md

@@ -355,33 +355,34 @@ The `:cache_hits` key is only included if the collection is rendered with `cache
 
 #### `sql.active_record`
 
-| Key                  | Value                                    |
-| -------------------- | ---------------------------------------- |
-| `:sql`               | SQL statement                            |
-| `:name`              | Name of the operation                    |
-| `:connection`        | Connection object                        |
-| `:transaction`       | Current transaction, if any              |
-| `:binds`             | Bind parameters                          |
-| `:type_casted_binds` | Typecasted bind parameters               |
-| `:statement_name`    | SQL Statement name                       |
-| `:async`             | `true` if query is loaded asynchronously |
-| `:cached`            | `true` is added when cached queries used |
-| `:row_count`         | Number of rows returned by the query     |
-| `:affected_rows`     | Number of rows affected by the query     |
+| Key                  | Value                                                  |
+| -------------------- | ------------------------------------------------------ |
+| `:sql`               | SQL statement                                          |
+| `:name`              | Name of the operation                                  |
+| `:binds`             | Bind parameters                                        |
+| `:type_casted_binds` | Typecasted bind parameters                             |
+| `:async`             | `true` if query is loaded asynchronously               |
+| `:connection`        | Connection object                                      |
+| `:transaction`       | Current transaction, if any                            |
+| `:affected_rows`     | Number of rows affected by the query                   |
+| `:row_count`         | Number of rows returned by the query                   |
+| `:cached`            | `true` is added when result comes from the query cache |
+| `:statement_name`    | SQL Statement name (Postgres only)                     |
 
 Adapters may add their own data as well.
 
 ```ruby
 {
   sql: "SELECT \"posts\".* FROM \"posts\" ",
   name: "Post Load",
-  connection: <ActiveRecord::ConnectionAdapters::SQLite3Adapter:0x00007f9f7a838850>,
-  transaction: <ActiveRecord::ConnectionAdapters::RealTransaction:0x0000000121b5d3e0>
   binds: [<ActiveModel::Attribute::WithCastValue:0x00007fe19d15dc00>],
   type_casted_binds: [11],
-  statement_name: nil,
-  row_count: 5,
+  async: false,
+  connection: <ActiveRecord::ConnectionAdapters::SQLite3Adapter:0x00007f9f7a838850>,
+  transaction: <ActiveRecord::ConnectionAdapters::RealTransaction:0x0000000121b5d3e0>
   affected_rows: 0
+  row_count: 5,
+  statement_name: nil,
 }
 ```