Prevent console.warn from getting logged during testing

[joebuono]

Description of changes

Updated Tabs tests to prevent console.warn from getting logged during testing.

I tried using the const originalWarn = console.warn trick, but I got the following error:

   Matcher error: received value must be a mock or spy function

    Received has type:  function
    Received has value: [Function warn]

I found a way to use .mockImplementation(), which worked: jest.fn() value must be a mock function or spy

Issue #, if available

Description of how you validated changes

Ran yarn test locally.

Checklist

• PR description included
• yarn test passes
• Tests are updated

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

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[zchenwei]

LGTM