chore(tests/dummy/app/templates): don't override classNames.

Author: matthewhartstonge

tests/dummy/app/templates/catalog.hbs

@@ -1297,7 +1297,7 @@
             <PaperSidenavToggle @name='left' as |toggleAction|>
               <PaperButton
                 @raised={{true}}
-                @classNames='hide-gt-sm'
+                @class='hide-gt-sm'
                 @onClick={{toggleAction}}
               >
                 Toggle left sidenav

tests/dummy/app/templates/demo/divider.hbs

@@ -51,7 +51,7 @@
         <CodeSnippet @name="divider.inset.hbs" />
       </div>
       {{! BEGIN-SNIPPET divider.inset }}
-      <PaperList @classNames="list-demo">
+      <PaperList @class="list-demo">
         {{#each this.messages as |item index|}}
           <PaperItem @class="md-3-line">
             <img src="/{{item.face}}?{{index}}" class="face" alt={{item.who}}>

tests/dummy/app/templates/demo/sidenav.hbs

@@ -45,7 +45,7 @@
             </p>
 
             <PaperSidenavToggle @name="left" as |toggleAction|>
-              <PaperButton @raised={{true}} @classNames="hide-gt-sm" @onClick={{action toggleAction}}>
+              <PaperButton @raised={{true}} @class="hide-gt-sm" @onClick={{action toggleAction}}>
                 Toggle left sidenav
               </PaperButton>
             </PaperSidenavToggle>