Make ImageData(Uint8ClampedArray)'s 3rd param optional (#790)

It can be inferred from the first two.

Author: sandersn

baselines/dom.generated.d.ts

@@ -9762,7 +9762,7 @@ interface ImageData {
 declare var ImageData: {
     prototype: ImageData;
     new(width: number, height: number): ImageData;
-    new(array: Uint8ClampedArray, width: number, height: number): ImageData;
+    new(array: Uint8ClampedArray, width: number, height?: number): ImageData;
 };
 
 interface InnerHTML {

baselines/webworker.generated.d.ts

@@ -2202,7 +2202,7 @@ interface ImageData {
 declare var ImageData: {
     prototype: ImageData;
     new(width: number, height: number): ImageData;
-    new(array: Uint8ClampedArray, width: number, height: number): ImageData;
+    new(array: Uint8ClampedArray, width: number, height?: number): ImageData;
 };
 
 /** This Channel Messaging API interface allows us to create a new message channel and send data through it via its two MessagePort properties. */

inputfiles/overridingTypes.json

@@ -1066,7 +1066,7 @@
                 "constructor": {
                     "override-signatures": [
                         "new(width: number, height: number): ImageData",
-                        "new(array: Uint8ClampedArray, width: number, height: number): ImageData"
+                        "new(array: Uint8ClampedArray, width: number, height?: number): ImageData"
                     ]
                 }
             },