Fix indentation and quotes in demos [skip ci]

Author: web-padawan

demo/dialog-basic-demos.html

@@ -1,14 +1,14 @@
 <dom-module id="dialog-basic-demos">
   <template>
     <style include="vaadin-component-demo-shared-styles">
-       :host {
+      :host {
         display: block;
       }
     </style>
 
 
     <h3>Simple Dialog</h3>
-    <vaadin-demo-snippet id='dialog-basic-demos-simple-dialog'>
+    <vaadin-demo-snippet id="dialog-basic-demos-simple-dialog">
       <template preserve-content>
         <dom-bind id="simple-dialog-example">
           <template>
@@ -34,7 +34,7 @@ <h3>Simple Dialog</h3>
 
 
     <h3>A Dialog That Can Only Be Closed with Buttons Inside It</h3>
-    <vaadin-demo-snippet id='dialog-basic-demos-a-dialog-that-can-only-be-closed-with-buttons-inside-it'>
+    <vaadin-demo-snippet id="dialog-basic-demos-a-dialog-that-can-only-be-closed-with-buttons-inside-it">
       <template preserve-content>
         <dom-bind id="dialog-example">
           <template>