Fix deleting providers

src/Readarr.Api.V1/ProviderControllerBase.cs

@@ -100,9 +100,10 @@ private TProviderDefinition GetDefinition(TProviderResource providerResource, bo
         }
 
         [RestDeleteById]
-        public void DeleteProvider(int id)
+        public object DeleteProvider(int id)
         {
             _providerFactory.Delete(id);
+            return new object();
         }
 
         [HttpGet("schema")]