Remove conflicting anchor targets from the sidebar

These are unnecessary and break linking on pages with identical section
titles.

Task-number: QTBUG-70435
Change-Id: I86f2b94253fc9217bc5b197d03c7018a94c717c6
Reviewed-by: Kai Koehne <kai.koehne@qt.io>

doc/config/style/qt5-sidebar.html

 <div class="sectionlist normallist">
     <div class="heading">
-        <a name="reference"></a>
-        <h2 id="reference">Reference</h2>
+        <h2>Reference</h2>
     </div>
     <div class="indexboxcont indexboxbar">
         <ul>
@@ -17,8 +16,7 @@
 </div>
 <div class="sectionlist normallist">
     <div class="heading">
-        <a name="getting-started"></a>
-        <h2 id="getting-started">Getting Started</h2>
+        <h2>Getting Started</h2>
     </div>
     <ul>
         <li><a href="gettingstarted.html">Getting Started with Qt</a></li>
@@ -30,8 +28,7 @@
 </div>
 <div class="sectionlist normallist">
     <div class="heading">
-        <a name="overviews"></a>
-        <h2 id="overviews">Overviews</h2>
+        <h2>Overviews</h2>
     </div>
     <ul>
         <li><a href="topics-app-development.html">Development Tools</a></li>