Don't warn when a flag is missing

It's totally legitimate to reference a feature flag that doesn't exist,
yet, but before this change, doing so would spam our logs with warnings.

flags/flags.go

@@ -134,9 +134,6 @@ func lookupDefault(context *ldcontext.Context, name string, defaultVal bool) boo
 	// BoolVariation and friends only return an error in the event that flags are
 	// not available (e.g. if LaunchDarkly is having an outage or we've
 	// misconfigured the client).
-	result, err := currentClient.BoolVariation(name, *context, defaultVal)
-	if err != nil {
-		log.Warnf("Failed to fetch value for flag '%s' (returning default %v to caller): %v", name, defaultVal, err)
-	}
+	result, _ := currentClient.BoolVariation(name, *context, defaultVal)
 	return result
 }