remove unnecessary heading-anchor

residue from when the heading text itself was a link

the id is on the header tag itself,
and the link is anchor-link

IPython/html/static/notebook/js/textcell.js

@@ -522,17 +522,10 var IPython = (function (IPython) {
             text = IPython.mathjaxutils.remove_math(text);
             var html = marked.parser(marked.lexer(text));
             var h = $(IPython.mathjaxutils.replace_math(html));
-            // move the markdown-rendered html down one level,
-            // into an anchor tag for linking
-            html = h.html();
-            var hash = h.text().replace(/ /g, '_');
-            h.empty();
-            var a = $('<a/>')
-                .addClass('heading-anchor')
-                .html(html)
-                .attr('id', hash);
-            // and append two anchors (one with the text, one clickable)
-            h.append(a).append(
+            // add id and linkback anchor
+            var hash = h.text().replace(/ /g, '-');
+            h.attr('id', hash);
+            h.append(
                 $('<a/>')
                     .addClass('anchor-link')
                     .attr('href', '#' + hash)

IPython/html/static/notebook/less/textcell.less

@@ -19,11 +19,6 div.text_cell_render {
     color: @textColor;
 }
 
-a.heading-anchor {
-  text-decoration: none;
-  color: inherit;
-}
-
 a.anchor-link:link {
   text-decoration: none;
   padding: 0px 20px;

IPython/html/static/style/style.min.css

@@ -1551,7 +1551,6 span#checkpoint_status,span#autosave_status{font-size:small;}
 @media (max-width:767px){span#save_widget{font-size:small;} span#checkpoint_status,span#autosave_status{font-size:x-small;}}@media (max-width:767px){span#checkpoint_status,span#autosave_status{display:none;}}@media (min-width:768px) and (max-width:979px){span#checkpoint_status{display:none;} span#autosave_status{font-size:x-small;}}div.text_cell{padding:5px 5px 5px 5px;}
 div.text_cell_input{color:#000000;border:1px solid #cfcfcf;border-radius:4px;background:#f7f7f7;}
 div.text_cell_render{outline:none;resize:none;width:inherit;border-style:none;padding:5px;color:#000000;}
-a.heading-anchor{text-decoration:none;color:inherit;}
 a.anchor-link:link{text-decoration:none;padding:0px 20px;visibility:hidden;}
 h1:hover .anchor-link,h2:hover .anchor-link,h3:hover .anchor-link,h4:hover .anchor-link,h5:hover .anchor-link,h6:hover .anchor-link{visibility:visible;}
 .toolbar{padding:0px 10px;margin-top:-5px;}.toolbar select,.toolbar label{width:auto;height:26px;vertical-align:middle;margin-right:2px;margin-bottom:0px;display:inline;font-size:92%;margin-left:0.3em;margin-right:0.3em;padding:0px;padding-top:3px;}