Stop rendering text inside flex boxes.

sky/tests/layout/position-absolute.sky

 <import src="../resources/dump-as-render-tree.sky" />
 
 <style>
-  block, paragraph, flex {
+  block, p, flex {
     width: 100px;
     height: 100px;
     margin-bottom: 50px;
     /* Make it a positioning root. */
     transform: translate3d(0, 0, 0);
   }
   block { background: pink; }
-  paragraph {
+  p {
     background: orange;
-    display: paragraph;
   }
   flex {
     background: salmon;
     display: flex;
     flex-direction: row;
   }
   spacer {
     height: 30px;
     width: 30px;
     border: 5px solid purple;
     background: papayawhip;
   }
   absolute {
     position: absolute;
     width: 20px;
     height: 20px;
     background: green;
   }
 </style>
 <block>
   <spacer />
   <absolute />
   <spacer />
 </block>
 
-<paragraph>
+<p>
   <spacer />
   <absolute />
   <spacer />
-</paragraph>
+</p>
 
 <flex>
   <spacer />
   <absolute />
   <spacer />
 </flex>