Rollup merge of rust-lang#98709 - GuillaumeGomez:rm-decl-for-old-browsers, r=Dylan-DPC

Remove unneeded methods declaration for old web browsers

All these methods were not defined for IE mostly. But since we don't support it anymore, no need to keep them around.

cc ```@jsha```
r? ```@notriddle```

Author: matthiaskrgr

src/librustdoc/html/static/js/main.js

@@ -4,40 +4,6 @@
 
 "use strict";
 
-if (!String.prototype.startsWith) {
-    String.prototype.startsWith = function(searchString, position) {
-        position = position || 0;
-        return this.indexOf(searchString, position) === position;
-    };
-}
-if (!String.prototype.endsWith) {
-    String.prototype.endsWith = function(suffix, length) {
-        const l = length || this.length;
-        return this.indexOf(suffix, l - suffix.length) !== -1;
-    };
-}
-
-if (!DOMTokenList.prototype.add) {
-    DOMTokenList.prototype.add = function(className) {
-        if (className && !hasClass(this, className)) {
-            if (this.className && this.className.length > 0) {
-                this.className += " " + className;
-            } else {
-                this.className = className;
-            }
-        }
-    };
-}
-
-if (!DOMTokenList.prototype.remove) {
-    DOMTokenList.prototype.remove = function(className) {
-        if (className && this.className) {
-            this.className = (" " + this.className + " ").replace(" " + className + " ", " ")
-                                                         .trim();
-        }
-    };
-}
-
 // Get a value from the rustdoc-vars div, which is used to convey data from
 // Rust to the JS. If there is no such element, return null.
 function getVar(name) {