fix(docs, chips): fixed small typo

Closes #5226

src/components/chips/js/chipsDirective.js

@@ -64,7 +64,7 @@
    * @param {string=|object=} ng-model A model to bind the list of items to
    * @param {string=} placeholder Placeholder text that will be forwarded to the input.
    * @param {string=} secondary-placeholder Placeholder text that will be forwarded to the input,
-   *    displayed when there is at least on item in the list
+   *    displayed when there is at least one item in the list
    * @param {boolean=} readonly Disables list manipulation (deleting or adding list items), hiding
    *    the input and delete buttons
    * @param {expression} md-transform-chip An expression of form `myFunction($chip)` that when called