Add missing word in speech-to-text.md

[superhindupur]

There was a missing word in the documentation that I added to make the sentence grammatically correct.

[prmerger-automator[bot]]

@superhindupur : Thanks for your contribution! The author(s) have been notified to review your proposed change.

[learn-build-service-prod[bot]]

Learn Build status updates of commit 9fcd6ef:

:white_check_mark: Validation status: passed

File	Status	Preview URL	Details
articles/ai-services/speech-service/speech-to-text.md	:white_check_mark:Succeeded

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[Court72]

@eric-urban

Can you review the proposed changes?

Important: When the changes are ready for publication, adding a #sign-off comment is the best way to signal that the PR is ready for the review team to merge.

#label:"aq-pr-triaged" @MicrosoftDocs/public-repo-pr-review-team

[Court72]

The article has been updated, and this change no longer applies. If you'd still like to update the article, please open a new PR. Or if you believe this PR was closed by mistake, email the PublicPRs alias.