Fix invalid key in deploy-website.yml

[OpenByteDev]

Why are these changes needed?

path when it should be paths, see https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-syntax#example-including-paths.

Related issue number

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• I've used pre-commit to lint the changes in this PR (note the same in integrated in our CI checks).
• I've included any doc changes needed for https://microsoft.github.io/FLAML/. See https://microsoft.github.io/FLAML/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
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[jianglibigdata]

LGTM!

[thinkall]

Good catch, thanks!