[css-text-decor-3] Fix more links

Author: fantasai

css-text-decor-3/Overview.html

@@ -1233,8 +1233,8 @@ <h2 class="heading settled" data-level="4" id="text-shadow-property"><span class
       <td><a href="https://www.w3.org/TR/css-transitions-1/#animtype-shadow-list">shadow list</a> 
    </table>
    <p>This property accepts a comma-separated list of shadow effects to
-    be applied to the text of the element. Values are interpreted as for <a class="property" data-link-type="propdesc" href="https://www.w3.org/TR/css-background-3/#propdef-box-shadow" id="ref-for-propdef-box-shadow">box-shadow</a> <a data-link-type="biblio" href="#biblio-css-backgrounds-3">[CSS-BACKGROUNDS-3]</a>.
-    (But note that spread values and the <a class="css" data-link-type="maybe" href="https://www.w3.org/TR/css-background-3/#shadow-inset" id="ref-for-shadow-inset">inset</a> keyword are not allowed.)
+    be applied to the text of the element. Values are interpreted as for <a class="property" data-link-type="propdesc" href="https://www.w3.org/TR/css-backgrounds-3/#propdef-box-shadow" id="ref-for-propdef-box-shadow">box-shadow</a> <a data-link-type="biblio" href="#biblio-css-backgrounds-3">[CSS-BACKGROUNDS-3]</a>.
+    (But note that spread values and the <a class="css" data-link-type="maybe" href="https://www.w3.org/TR/css-backgrounds-3/#shadow-inset" id="ref-for-shadow-inset">inset</a> keyword are not allowed.)
     Each layer shadows the element’s text and all its text decorations
     (composited together).
     If the color of the shadow is not specified,
@@ -1252,7 +1252,7 @@ <h2 class="heading settled" data-level="4" id="text-shadow-property"><span class
     It is undefined whether a given shadow layer shadows
     each glyph or decoration independently
     or if the text and/or decorations are flattened and then shadowed. </p>
-   <p>Unlike <a class="property" data-link-type="propdesc" href="https://www.w3.org/TR/css-background-3/#propdef-box-shadow" id="ref-for-propdef-box-shadow①">box-shadow</a>, text shadows are not clipped to the shadowed
+   <p>Unlike <a class="property" data-link-type="propdesc" href="https://www.w3.org/TR/css-backgrounds-3/#propdef-box-shadow" id="ref-for-propdef-box-shadow①">box-shadow</a>, text shadows are not clipped to the shadowed
     shape and may show through if the text is partially-transparent.
     Like <span class="property">box-shadow</span>, text shadows do not influence layout, and do not
     trigger scrolling or increase the size of the scrollable area. </p>