Align definitions with new definition of entity. Related to #463.

Author: msporny

terms.html

@@ -124,7 +124,7 @@
   </dd>
   <dt><dfn data-lt="subjects|subject's">subject</dfn></dt>
   <dd>
-An <a>entity</a> about which <a>claims</a> are made.
+A thing about which <a>claims</a> are made.
   </dd>
   <dt><dfn>user agent</dfn></dt>
   <dd>