style(guide/css-styling): remove trailing whitespace

Pretty self-explanatory, no mystery here.

Author: caitp

docs/content/guide/css-styling.ngdoc

@@ -13,8 +13,8 @@ Angular sets these CSS classes. It is up to your application to provide useful s
     is defined. (see {@link guide/scope scope} guide for more information about scopes)
 
 * `ng-isolate-scope`
-  - **Usage:** angular applies this class to any element for which a new 
-    {@link guide/directive#isolating-the-scope-of-a-directive isolate scope} is defined. 
+  - **Usage:** angular applies this class to any element for which a new
+    {@link guide/directive#isolating-the-scope-of-a-directive isolate scope} is defined.
 
 * `ng-binding`
   - **Usage:** angular applies this class to any element that is attached to a data binding, via `ng-bind` or
@@ -28,7 +28,7 @@ Angular sets these CSS classes. It is up to your application to provide useful s
   - **Usage:** angular {@link ng.directive:input input} directive applies `ng-pristine` class
     to a new input widget element which did not have user interaction. Once the user interacts with
     the input widget the class is changed to `ng-dirty`.
-    
+
 * `ng-touched`, `ng-untouched`
   - **Usage:** angular {@link ng.directive:ngModel ngModel} directive applies `ng-untouched` class
     to a new input widget element which has not been blurred. Once the user blurs the input widget