Fix VS only warning (#39614)

https://github.com/dotnet/aspnetcore/blob/1ca07094ce3827229658c8abb741a9c3bc1fd9ae/.editorconfig#L233-L234 was missed in this file

src/Servers/Kestrel/Core/src/Internal/Http/HttpParser.cs

@@ -144,7 +144,7 @@ public class HttpParser<TRequestHandler> : IHttpParser<TRequestHandler> where TR
             var span = reader.UnreadSpan;
             while (span.Length > 0)
             {
-                var ch1 = (byte)0;
+                byte ch1;
                 var ch2 = (byte)0;
                 var readAhead = 0;