refactor(remove): schema cache load delay config

Remove internal schema cache load and relationship load sleep settings plus
the delay wrappers they enabled. Drop IO tests that depended on the removed
settings.

src/PostgREST/Config.hs

@@ -127,8 +127,6 @@ data AppConfig = AppConfig
   , configRoleSettings             :: RoleSettings
   , configRoleIsoLvl               :: RoleIsolationLvl
   , configInternalSCQuerySleep     :: Maybe Int32
-  , configInternalSCLoadSleep      :: Maybe Int32
-  , configInternalSCRelLoadSleep   :: Maybe Int32
   }
 
 data LogLevel = LogCrit | LogError | LogWarn | LogInfo | LogDebug
@@ -328,8 +326,6 @@ parser optPath env dbSettings roleSettings roleIsolationLvl =
     <*> pure roleSettings
     <*> pure roleIsolationLvl
     <*> optInt "internal-schema-cache-query-sleep"
-    <*> optInt "internal-schema-cache-load-sleep"
-    <*> optInt "internal-schema-cache-relationship-load-sleep"
   where
     parseErrorVerbosity :: C.Key -> C.Parser C.Config Verbosity
     parseErrorVerbosity k =