Playwright: don't use junit inside Sketch.

I've found Sketch doesn't understand the JUnit failure nearly
as well as the usual way.
diff --git a/webui/playwright-ct.config.ts b/webui/playwright-ct.config.ts
index 8f75fcd..4dc1982 100644
--- a/webui/playwright-ct.config.ts
+++ b/webui/playwright-ct.config.ts
@@ -50,9 +50,7 @@
 });
 
 function getReporterConfig(): PlaywrightTestConfig["reporter"] {
-  if (process.env.SKETCH) {
-    return [["junit"]];
-  }
-
+  // Sketch does not understand the junit failure reporting very well.
+  
   return [["html", { open: "never" }]];
 }