Add deprecated field to supported fields (#875)

* Add deprecated field to supported fields

* Update spec/spec.go

Co-authored-by: anniel-stripe <97691964+anniel-stripe@users.noreply.github.com>

---------

Co-authored-by: anniel-stripe <97691964+anniel-stripe@users.noreply.github.com>

Author: helenye-stripe

spec/spec.go

@@ -85,6 +85,9 @@ var supportedSchemaFields = []string{
 	"x-stripeOperations",
 	"x-stripeParam",
 	"x-stripeEvent",
+	// This isn't used in our SDK, but is additional metadata unnecessary for
+	// stripe-mock.
+	"deprecated",
 
 	// This is currently a hint for the server-side so I haven't included it in
 	// Schema yet. If we do start validating responses that come out of