Bug 1840214 - Disable inset box-shadow zero blur clips on new clip-path r=gfx-reviewers,lsalzman

This is causing some issues and we're close to release, do disable
this rare case on the new path for now.

Differential Revision: https://phabricator.services.mozilla.com/D181946

gfx/wr/webrender/src/prepare.rs

@@ -125,6 +125,10 @@ fn can_use_clip_chain_for_quad_path(
         }
 
         match clip_node.item.kind {
+            ClipItemKind::Rectangle { mode: ClipMode::ClipOut, .. } |
+            ClipItemKind::RoundedRectangle { mode: ClipMode::ClipOut, .. } => {
+                return false;
+            }
             ClipItemKind::RoundedRectangle { .. } | ClipItemKind::Rectangle { .. } => {}
             ClipItemKind::BoxShadow { .. } => {
                 // legacy path for box-shadows for now (move them to a separate primitive next)