Turn off spvc being used by default

There appears to be issues with the CTS + spvc that are preventing
chromium to roll, so I am reverting spvc by default, until the CTS
issues are resolved.

BUG=dawn:337

Change-Id: I171ee5325b9afbf5d240a469009433105caf6ddb
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/15840
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
diff --git a/src/dawn_native/Device.cpp b/src/dawn_native/Device.cpp
index cabea0f..6e41e56 100644
--- a/src/dawn_native/Device.cpp
+++ b/src/dawn_native/Device.cpp
@@ -692,7 +692,6 @@
     void DeviceBase::SetDefaultToggles() {
         // Sets the default-enabled toggles
         mTogglesSet.SetToggle(Toggle::LazyClearResourceOnFirstUse, true);
-        mTogglesSet.SetToggle(Toggle::UseSpvc, true);
     }
 
     // Implementation details of object creation