In card message: set the text color on the body text view (#3286)

* In card message: set the text color on the body text view

* Fix bug where card messages in test app were showing up with two of the same buttons

* Revert change to text color

InAppMessagingDisplay/Example/FiamDisplaySwiftExample/CardMessageViewController.swift

@@ -62,7 +62,7 @@ class CardMessageViewController: CommonMessageTestVC {
     }
 
     override var secondaryActionButton: InAppMessagingActionButton? {
-      return writablePrimaryActionButton
+      return writableSecondaryActionButton
     }
 
     override var secondaryActionURL: URL? {