Fix static analysis issue with ProtocolType

Author: jessicl-ms

src/FrontDoor/FrontDoor/Models/PSFrontendEndpoint.cs

@@ -35,7 +35,7 @@ public class PSFrontendEndpoint : PSResource
 
         public string CertificateSource { get; set; }
 
-        public string ProtocolType = "ServerNameIndication";
+        public string ProtocolType { get; set; } = "ServerNameIndication";
 
         public string MinimumTlsVersion { get; set; }