fix: trace viewer with global applied background-color (#23362)

Fixes https://github.com/microsoft/playwright/issues/23275

packages/playwright-core/src/server/injected/highlight.ts

@@ -53,6 +53,7 @@ export class Highlight {
     this._glassPaneElement.style.zIndex = '2147483647';
     this._glassPaneElement.style.pointerEvents = 'none';
     this._glassPaneElement.style.display = 'flex';
+    this._glassPaneElement.style.backgroundColor = 'transparent';
 
     this._actionPointElement = document.createElement('x-pw-action-point');
     this._actionPointElement.setAttribute('hidden', 'true');