fix: deprecation warning fix (#317)

Signed-off-by: jamesmilligan <[email protected]>

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## This PR
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- fixes incorrect default on deprecation warning, preventing warning log
when the flag is not used

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Signed-off-by: jamesmilligan <[email protected]>
Co-authored-by: Michael Beemer <[email protected]>

cmd/start.go

@@ -95,7 +95,7 @@ var startCmd = &cobra.Command{
 				"Docs: https://github.com/open-feature/flagd/blob/main/docs/configuration.md")
 		}
 
-		if viper.GetString(evaluatorFlagName) != "" {
+		if viper.GetString(evaluatorFlagName) != "json" {
 			rtLogger.Warn("DEPRECATED: The --evaluator flag has been deprecated. " +
 				"Docs: https://github.com/open-feature/flagd/blob/main/docs/configuration.md")
 		}