fix: inaccurate Server-Timing durations

The transaction duration was notably off, doing:

```
curl localhost:3000/rpc/sleep?seconds=5 -i
```

Shows `46.1` for the `transaction;dur`, with this fix we obtain
`5007.3`.

Fixes https://github.com/PostgREST/postgrest/issues/4522

This also fixes inaccurate "schema cache queried" logs,
see https://github.com/PostgREST/postgrest/issues/4551.

src/PostgREST/AppState.hs

@@ -44,8 +44,8 @@ import qualified PostgREST.Error            as Error
 import qualified PostgREST.Logger           as Logger
 import qualified PostgREST.Metrics          as Metrics
 import           PostgREST.Observation
+import           PostgREST.TimeIt           (timeItT)
 import           PostgREST.Version          (prettyVersion)
-import           System.TimeIt              (timeItT)
 
 import Control.AutoUpdate (defaultUpdateSettings, mkAutoUpdate,
                            updateAction)