fix: WebMCP Evals readme with correct execution command

[dinesh-kumar-allen]

No description provided.

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[andreban]

@dinesh-kumar-allen thank you for catching this and sending a PR. We'll need you to accept the CLA (https://cla.developers.google.com/) to be able to merge your contribution.

[dinesh-kumar-allen]

@dinesh-kumar-allen thank you for catching this and sending a PR. We'll need you to accept the CLA (https://cla.developers.google.com/) to be able to merge your contribution.

@andreban Yes, I have accepted the CLA.

[andreban]

LGTM, thank you!