Standardise on a single blit function

Keep everything simpler by always blitting in the same pixel format.
It's up to the decoders to convert if they need to.

kasmweb/core/util/browser.js

@@ -45,15 +45,6 @@ try {
 
 export const supportsCursorURIs = _supportsCursorURIs;
 
-let _supportsImageMetadata = false;
-try {
-    new ImageData(new Uint8ClampedArray(4), 1, 1);
-    _supportsImageMetadata = true;
-} catch (ex) {
-    // ignore failure
-}
-export const supportsImageMetadata = _supportsImageMetadata;
-
 let _hasScrollbarGutter = true;
 try {
     // Create invisible container