docs: fix return jsdoc type of titlePath (#4886)

Co-authored-by: Josh Goldberg ✨ <[email protected]>

Author: F3n67u

lib/runnable.js

@@ -211,7 +211,7 @@ Runnable.prototype.fullTitle = function () {
  *
  * @memberof Mocha.Runnable
  * @public
- * @return {string}
+ * @return {string[]}
  */
 Runnable.prototype.titlePath = function () {
   return this.parent.titlePath().concat([this.title]);

lib/suite.js

@@ -387,7 +387,7 @@ Suite.prototype.fullTitle = function () {
  *
  * @memberof Suite
  * @public
- * @return {string}
+ * @return {string[]}
  */
 Suite.prototype.titlePath = function () {
   var result = [];