Fix Transforms documentation

[joegoldman2]

The current example is throwing the following exception:

System.AggregateException: The proxy config is invalid. (Unexpected value for X-Forwarded: proto,host,for,prefix. Expected one of ForwardedTransformActions) (Unexpected value for Prefix: X-Forwarded-. Expected one of ForwardedTransformActions) (The transform contains more parameters than expected: Append;Prefix;X-Forwarded)
       ---> System.ArgumentException: Unexpected value for X-Forwarded: proto,host,for,prefix. Expected one of ForwardedTransformActions