Remove extra js in docs

Since the release of Read the Docs 2.5 this is no longer required
and it broke version selector.

docs/extra/extra.js

@@ -1,57 +0,0 @@
-var nodemcu = nodemcu || {};
-(function () {
-    'use strict';
-
-    $(document).ready(function () {
-        fixSearch();
-    });
-
-    /*
-     * RTD messes up MkDocs' search feature by tinkering with the search box defined in the theme, see
-     * https://github.com/rtfd/readthedocs.org/issues/1088. This function sets up a DOM4 MutationObserver
-     * to react to changes to the search form (triggered by RTD on doc ready). It then reverts everything
-     * the RTD JS code modified.
-     */
-    function fixSearch() {
-        var target = document.getElementById('rtd-search-form');
-        var config = {attributes: true, childList: true};
-
-        var observer = new MutationObserver(function (mutations) {
-            // if it isn't disconnected it'll loop infinitely because the observed element is modified
-            observer.disconnect();
-            var form = $('#rtd-search-form');
-            form.empty();
-            form.attr('action', 'https://' + window.location.hostname + '/en/' + determineSelectedBranch() + '/search.html');
-            $('<input>').attr({
-                type: "text",
-                name: "q",
-                placeholder: "Search docs"
-            }).appendTo(form);
-        });
-
-        if (window.location.origin.indexOf('readthedocs') > -1) {
-            observer.observe(target, config);
-        }
-    }
-
-    /**
-     * Analyzes the URL of the current page to find out what the selected GitHub branch is. It's usually
-     * part of the location path. The code needs to distinguish between running MkDocs standalone
-     * and docs served from RTD. If no valid branch could be determined 'dev' returned.
-     *
-     * @returns GitHub branch name
-     */
-    function determineSelectedBranch() {
-        var branch = 'dev', path = window.location.pathname;
-        if (window.location.origin.indexOf('readthedocs') > -1) {
-            // path is like /en/<branch>/<lang>/build/ -> extract 'lang'
-            // split[0] is an '' because the path starts with the separator
-            var thirdPathSegment = path.split('/')[2];
-            // 'latest' is an alias on RTD for the 'dev' branch - which is the default for 'branch' here
-            if (thirdPathSegment !== 'latest') {
-                branch = thirdPathSegment;
-            }
-        }
-        return branch;
-    }
-}());

mkdocs.yml

@@ -5,7 +5,3 @@ edit_uri: edit/develop/docs/
 theme: readthedocs
 extra_css:
     - extra/extra.css
-
-extra_javascript:
-    - extra/extra.js
-