remove type() from prefixed code.

Author: estelle

images/image-set-type.html

@@ -17,8 +17,8 @@
     <style class="editable">
        .box {
           background-image: -webkit-image-set(
-            url("large-balloons.avif") type("image/avif"),
-            url("large-balloons.jpg") type("image/jpeg"));
+            url("large-balloons.avif"),
+            url("large-balloons.jpg"));
           background-image: image-set(
             url("large-balloons.avif") type("image/avif"),
             url("large-balloons.jpg") type("image/jpeg"));
@@ -34,8 +34,8 @@
     <textarea class="playable playable-css" style="height: 155px;">
 .box {
   background-image: -webkit-image-set(
-    url("large-balloons.avif") type("image/avif"),
-    url("large-balloons.jpg") type("image/jpeg"));
+    url("large-balloons.avif"),
+    url("large-balloons.jpg"));
   background-image: image-set(
     url("large-balloons.avif") type("image/avif"),
     url("large-balloons.jpg") type("image/jpeg"));