Fixed typo - fourth instead if forth

[vsobotka]

Hi, I was looking for something in the source and stumbled on this typo.

[mention-bot]

@vsobotka, thanks for your PR! By analyzing the history of the files in this pull request, we identified @egamma and @jrieken to be potential reviewers.

[msftclas]

@vsobotka,
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Thanks,
Microsoft Pull Request Bot

[msftclas]

@vsobotka, thanks for signing the contribution license agreement. We will now validate the agreement and then the pull request.

Thanks, Microsoft Pull Request Bot

[jrieken]

Thanks