Remove implicit anchor from position-anchor demo

Author: jamesnw

index.html

@@ -321,15 +321,13 @@ <h2>
         <div
           id="my-position-target-a"
           class="target"
-          anchor="my-implicit-anchor"
         >
           Target A
         </div>
         <div id="my-position-anchor-b" class="anchor">Anchor B</div>
         <div
           id="my-position-target-b"
           class="target"
-          anchor="my-implicit-anchor"
         >
           Target B
         </div>