CTS expectations: Add KEEP on [ Skip ]'d rules

Without this, the next update will rebuild these expectations, without the Skip.
They appear to be flakey, preventing rolls from landing.

Change-Id: I09eacf9596fd4d984e2c6ac600076dbaeafe5347
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/114700
Auto-Submit: Ben Clayton <bclayton@google.com>
Reviewed-by: Austin Eng <enga@chromium.org>
Kokoro: Ben Clayton <bclayton@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
diff --git a/webgpu-cts/expectations.txt b/webgpu-cts/expectations.txt
index 804c40e..0f35c12 100644
--- a/webgpu-cts/expectations.txt
+++ b/webgpu-cts/expectations.txt
@@ -444,6 +444,7 @@
 
 ################################################################################
 # commandEncoder validation tests need updates in CTS
+# KEEP
 ################################################################################
 crbug.com/dawn/1602 webgpu:api,validation,encoding,beginComputePass:* [ Skip ]
 crbug.com/dawn/1602 webgpu:api,validation,encoding,beginRenderPass:* [ Skip ]