docs(demos): clean up some of the demo markup

references #5311

demos/buttons/main.html

@@ -3,29 +3,28 @@
   <ion-title>Buttons</ion-title>
 </ion-toolbar>
 
-<ion-content padding style="text-align:center">
-
+<ion-content text-center>
 
   <h4>Colors</h4>
 
   <p>
-    <button block>Default</button>
+    <button>Default</button>
   </p>
 
   <p>
-    <button secondary block>Secondary</button>
+    <button secondary>Secondary</button>
   </p>
 
   <p>
-    <button danger block>Danger</button>
+    <button danger>Danger</button>
   </p>
 
   <p>
-    <button light block>Light</button>
+    <button light>Light</button>
   </p>
 
   <p>
-    <button dark block>Dark</button>
+    <button dark>Dark</button>
   </p>
 
   <h4>Shapes</h4>

demos/config/main.html

@@ -50,7 +50,7 @@
 })</pre>
 
   <div padding>
-    <button block light (click)="push()">
+    <button block secondary (click)="push()">
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     </button>
   </div>