docs($injector): clean up docs for $injector#has

Fixup return type and param info.

Closes angular#9452

Author: thorn0

src/auto/injector.js

@@ -201,8 +201,8 @@ function annotate(fn, strictDi, name) {
  * @description
  * Allows the user to query if the particular service exists.
  *
- * @param {string} Name of the service to query.
- * @returns {boolean} returns true if injector has given service.
+ * @param {string} name Name of the service to query.
+ * @returns {boolean} `true` if injector has given service.
  */
 
 /**