Remove stale WebGPU CTS expectations

Autogenerated CL from running:

//content/test/gpu/unexpected_pass_finder.py --project chrome-unexpected-pass-data --include-internal-builders --remove-stale-expectations --narrow-semi-stale-expectation-scope --num-samples 300 --suite webgpu_cts --jobs 2

Affected bugs for CL description:

R=rubber-stamper@appspot.gserviceaccount.com

Bug: dawn:1992
Change-Id: I34ec3ba5aff5c9e3b2af3d966b2b482c063e0fc2
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/160320
Kokoro: Kokoro <noreply+kokoro@google.com>
Bot-Commit: rubber-stamper@appspot.gserviceaccount.com <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: chrome-automated-expectation@chops-service-accounts.iam.gserviceaccount.com <chrome-automated-expectation@chops-service-accounts.iam.gserviceaccount.com>
Commit-Queue: rubber-stamper@appspot.gserviceaccount.com <rubber-stamper@appspot.gserviceaccount.com>
diff --git a/webgpu-cts/expectations.txt b/webgpu-cts/expectations.txt
index bcfd071..e50d2fc 100644
--- a/webgpu-cts/expectations.txt
+++ b/webgpu-cts/expectations.txt
@@ -673,7 +673,6 @@
 # Shader f32 matrix tests failing on Android Qualcomm (Pixel 4)
 ################################################################################
 crbug.com/dawn/1992 [ android-r ] webgpu:shader,execution,expression,binary,f32_matrix_matrix_multiplication:* [ RetryOnFailure ]
-crbug.com/dawn/1992 [ android-r ] webgpu:shader,execution,expression,binary,f32_matrix_subtraction:* [ RetryOnFailure ]
 
 ################################################################################
 # Tint unimplemented feature