Revert "fix: slow responses on schema cache reload"

This reverts commit 727ef465c1.

Also documents requests waiting for the schema cache.

src/PostgREST/AppState.hs

@@ -320,12 +320,10 @@ loadSchemaCache appState observer = do
           return SCOnRetry
 
     Right sCache -> do
+      putSchemaCache appState $ Just sCache
       observer $ SchemaCacheQueriedObs resultTime
       (t, _) <- timeItT $ observer $ SchemaCacheSummaryObs sCache
       observer $ SchemaCacheLoadedObs t
-      -- it's important to update AppState schema cache only once it has been fully evaluated before (this will be done by the observer above)
-      -- otherwise requests will wait for the schema cache to be loaded
-      putSchemaCache appState $ Just sCache
       putSchemaCacheLoaded appState True
       return SCLoaded