[css-backgrounds-3][editorial] Remove 'Glossary' redefining terms already defined in other specs.

Author: tabatkins

css-backgrounds-3/Overview.bs

@@ -2513,43 +2513,14 @@ Layering, Layout, and Other Details</h4>
   or an inner shadow on a rowspanning table cell that adjoins cells with different border thicknesses),
   the exact position and rendering of its shadows are undefined
 
-<h2 id="definitions">Definitions</h2>
-
-
-<h3 id="glossary">Glossary</h3>
-
-<p>The following terms and abbreviations are used in this
-module.
-
-<dl>
-<dt><dfn>UA</dfn>
-<dt><dfn id="user-agent">user agent</dfn>
-<dd>
-<p>A program that reads and/or writes CSS style sheets on behalf of a
-user in either or both of these categories: programs whose purpose is
-to render <span>documents</span> (e.g., browsers) and
-programs whose purpose is to create style sheets (e.g., editors). A UA
-may fall into both categories. (There are other programs that read or
-write style sheets, but this module gives no rules for them.)
-
-<dt><dfn title="document|documents">document</dfn>
-<dd>
-<p>A tree-structured document with elements and attributes, such as an
-SGML or XML document [[XML11]].
-
-<dt><dfn>style sheet</dfn>
-<dd>
-<p>A <a href="https://www.w3.org/TR/CSS2/conform.html#style-sheet">CSS style sheet</a>.
-</dl>
-
-<h3 id="levels">Levels</h3>
+<h2 id="levels">Levels</h2>
 
 <p><em>This section is informative.</em> CSS has different levels of
 features, each a subset of the other.
 (See [[CSS-2017]] for a full explanation.)
 The lists below describe which features from this specification are in each level.
 
-<h4 id="level-1">Level 1</h4>
+<h3 id="level-1">Level 1</h3>
 <ul>
   <li>'background-color'
   <li>'background-image' only one image (no layers)
@@ -2563,7 +2534,7 @@ The lists below describe which features from this specification are in each leve
   <li>'border-top', 'border-bottom', 'border-right', 'border-left', and 'border' shorthands
 </ul>
 
-<h4 id="level-2">Level 2</h4>
+<h3 id="level-2">Level 2</h3>
 <ul>
   <li>'background-color'
   <li>'background-image': only one image (no layers)
@@ -2577,7 +2548,7 @@ The lists below describe which features from this specification are in each leve
   <li>'border-top', 'border-bottom', 'border-right', 'border-left', and 'border' shorthands
 </ul>
 
-<h4 id="level-3">Level 3</h4>
+<h3 id="level-3">Level 3</h3>
 <ul>
   <li>All features described in the CSS Backgrounds and Borders Module Level 3
 </ul>