remove separate definition of type secret as any to be used as fallback

Author: VShingala

lib/collection/variable.js

@@ -454,28 +454,6 @@ _.assign(Variable, /** @lends Variable */ {
             }
         },
 
-        /**
-         * A "secret" type variable indicates the value should be resolved from an external source
-         * using the `source` property.
-         */
-        secret: {
-            /**
-             * @param {*} val -
-             * @returns {*}
-             */
-            in (val) {
-                return val; // pass through
-            },
-
-            /**
-             * @param {*} val -
-             * @returns {*}
-             */
-            out (val) {
-                return val; // pass through
-            }
-        },
-
         /**
          * Free-form type of a value. This is the default for any variable, unless specified otherwise. It ensures that
          * the variable can store data in any type and no conversion is done while using {@link Variable#get}.