Just one Application Version header

(cherry picked from commit ab502ffda41aaae8bccaa4f33c62e3fca61b277f)

src/Radarr.Http/Extensions/Pipelines/RadarrVersionPipeline.cs

@@ -16,9 +16,9 @@ namespace Radarr.Http.Extensions.Pipelines
 
         private void Handle(NancyContext context)
         {
-            if (!context.Response.Headers.ContainsKey("X-ApplicationVersion"))
+            if (!context.Response.Headers.ContainsKey("X-Application-Version"))
             {
-                context.Response.Headers.Add("X-ApplicationVersion", BuildInfo.Version.ToString());
+                context.Response.Headers.Add("X-Application-Version", BuildInfo.Version.ToString());
             }
         }
     }