android_webview: update list of not-exposed interfaces for XR rename.

Follow-up to crrev.com/c/2055408

Bug: 1057130
Change-Id: I032dc071209ddaf46bf4e8f3ae2d3d3f20ee739e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2079685Reviewed-by: Bo <boliu@chromium.org>
Commit-Queue: John Budorick <jbudorick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#745532}

android_webview/tools/system_webview_shell/test/data/webexposed/not-webview-exposed.txt

@@ -134,7 +134,7 @@ interface WebGL2ComputeRenderingContext
 # WebXR dependent interfaces are not supported on WebView crbug.com/1012899
 interface XRView
 interface XRViewport
-interface XR : EventTarget
+interface XRSystem : EventTarget
 interface XRFrame
 interface XRRigidTransform
 interface XRSpace : EventTarget