Fix swapped definitions of title and text members.

The definitions of the `title` and `text` members of `ShareTargetParams`
were swapped; this associates the correct definition with the correct
member.

I got here from w3ctag/design-reviews#221.

Author: dbaron

index.html

@@ -311,12 +311,12 @@ <h3>
         </p>
         <p>
           The <dfn>title</dfn> member specifies the name of the query parameter
-          used for the arbitrary text that forms the body of the message being
-          shared.
+          used for the title of the document being shared.
         </p>
         <p>
           The <dfn>text</dfn> member specifies the name of the query parameter
-          used for the title of the document being shared.
+          used for the arbitrary text that forms the body of the message being
+          shared.
         </p>
         <p>
           The <dfn>url</dfn> member specifies the name of the query parameter