Hidden should only be used if not-configurable (#327)

Author: viceroypenguin

src/Immediate.Handlers.Analyzers/AnalyzerReleases.Shipped.md

@@ -43,7 +43,7 @@ IHR0015 | ImmediateHandler | Error | HandlerClassAnalyzer
 IHR0016 | ImmediateHandler | Warning | HandlerClassAnalyzer
 IHR0017 | ImmediateHandler | Warning | HandlerClassAnalyzer
 IHR0018 | ImmediateHandler | Warning | HandlerClassAnalyzer
-IHR0019 | ImmediateHandler | Hidden | HandlerClassAnalyzer
+IHR0019 | ImmediateHandler | Info | HandlerClassAnalyzer
 
 ### Removed Rules
 

src/Immediate.Handlers.Analyzers/HandlerClassAnalyzer.cs

@@ -142,7 +142,7 @@ public sealed class HandlerClassAnalyzer : DiagnosticAnalyzer
 			title: "Static handler may be converted to a sealed handler",
 			messageFormat: "Class '{0}' can be converted to be a `sealed` handler",
 			category: "ImmediateHandler",
-			defaultSeverity: DiagnosticSeverity.Hidden,
+			defaultSeverity: DiagnosticSeverity.Info,
 			isEnabledByDefault: true,
 			description: "Static handler may be converted to a sealed handler."
 		);