Remove pipeline statistics query tests

[beaufortfrancois]

This PR removes pipeline statistics query tests as it's not part of the WebGPU spec.

Requirements for PR author:

• All missing test coverage is tracked with "TODO" or .unimplemented().
• New helpers are /** documented */ and new helper files are found in helper_index.txt.
• Test behaves as expected in a WebGPU implementation. (If not passing, explain above.)

Requirements for reviewer sign-off:

• Tests are properly located in the test tree.
• Test descriptions allow a reader to "read only the test plans and evaluate coverage completeness", and accurately reflect the test code.
• Tests provide complete coverage (including validation control cases). Missing coverage MUST be covered by TODOs.
• Helpers and types promote readability and maintainability.

When landing this PR, be sure to make any necessary issue status updates.

[github-actions]

Previews, as seen when this build job started (f866762):
Run tests | View tsdoc

[github-actions]

Previews, as seen when this build job started (a8391fa):
Run tests | View tsdoc

[kainino0x]

I'm surprised you didn't have to remove it from capability_info.ts (it's already not there). I guess some of these test descriptions were wrong and they weren't even testing pipeline statistics queries to begin with.