Editorial: clarify where to get apps name from (#927)

* Editorial: clarify where to get apps name from

* Remove Authority section - closes #888

Co-authored-by: Marcos Cáceres <mcaceres@mozilla.com>
Co-authored-by: Aaron Gustafson <aaron@easy-designs.net>

index.html

@@ -269,40 +269,28 @@ <h2>
         it's a [=top-level browsing context=] and the user agent deems it to be
         installable (e.g., see [[[#installability-signals]]]).
       </p>
-      <section>
-        <h3>
-          Authority of the manifest's metadata
-        </h3>
-        <p>
-          When a <a>manifest</a> is linked from a {{Document}}, it indicates to
-          the user agent that the metadata is <dfn>authoritative</dfn>: that
-          is, the user agent SHOULD use the metadata of the manifest instead of
-          the one in the {{Document}}. However, in cases where metadata is
-          missing, or in error, a user agent MAY fallback to the {{Document}}
-          to find suitable replacements for missing manifest members (e.g.,
-          using `application-name` in place of `short_name`).
-        </p>
-      </section>
       <section data-link-for="WebAppManifest">
         <h3>
           Application's name
         </h3>
         <p>
           The <dfn>application's name</dfn> is derived from either the
-          <a>name</a> member or <a>short_name</a> member (if either is present)
-          - otherwise, it is generated by the user agent or provided by the
-          end-user.
+          <a>name</a> member or <a>short_name</a> member.
         </p>
         <p>
-          When either member is missing from the manifest, a user agent MAY use
-          the <a>name</a> member as a fallback for the <a>short_name</a> member
-          or vice versa.
+          When either the <a>name</a> member or the <a>short_name</a> member is
+          missing, a user agent MAY use the <a>name</a> member as a fallback
+          for the <a>short_name</a> member or <a>short_name</a> as the fallback
+          for the <a>name</a> member.
         </p>
         <p>
-          If the <a>name</a> and <a>short_name</a> members are undefined, the
-          user agent SHOULD assign a default name (e.g., "Untitled") that
-          follows platform conventions. Alternatively, a user agent MAY allow
-          the end-user to input some text that can serve as the
+          If the <a>name</a> and <a>short_name</a> members are missing or
+          undefined, a user agent MAY fallback to the {{Document}} to find
+          suitable replacements for missing manifest members (e.g., using
+          `application-name` in place of <a>name</a> or <a>short_name</a>).
+          Alternatively, the user agent SHOULD assign a default name (e.g.,
+          "Untitled") that follows platform conventions. Alternatively, a user
+          agent MAY allow the end-user to input some text that can serve as the
           <a>application's name</a>.
         </p>
         <p>