Removed the string indexers that return Element because of TypeScript limitation

Author: FranklinWhale

baselines/dom.generated.d.ts

@@ -4461,7 +4461,6 @@ interface HTMLCollection {
       */
     namedItem(name: string): Element;
     [index: number]: Element;
-    [name: string]: Element;
 }
 
 declare var HTMLCollection: {
@@ -13628,7 +13627,6 @@ interface HTMLCollectionOf<T extends Element> extends HTMLCollection {
     item(index: number): T;
     namedItem(name: string): T;
     [index: number]: T;
-    [name: string]: T;
 }
 
 interface BlobPropertyBag {

inputfiles/addedTypes.json

@@ -105,8 +105,7 @@
         "indexer": [
             {
                 "signatures": [
-                    "[index: number]: T",
-                    "[name: string]: T"
+                    "[index: number]: T"
                 ]
             }
         ]
@@ -213,8 +212,7 @@
         "kind": "indexer",
         "interface": "HTMLCollection",
         "signatures": [
-            "[index: number]: Element",
-            "[name: string]: Element"
+            "[index: number]: Element"
         ]
     },
     {