Update opentelemetry-dotnet-migrate.md to fix basic grammar

[react-o-licious]

Fix grammar

[prmerger-automator]

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

[learn-build-service-prod]

Learn Build status updates of commit 08bc0c5:

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[react-o-licious]

Cheers @AaronMaxwell

[learn-build-service-prod]

Learn Build status updates of commit 1dd6357:

✅ Validation status: passed

File	Status	Preview URL	Details
articles/azure-monitor/app/opentelemetry-dotnet-migrate.md	✅Succeeded

For more details, please refer to the build report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel

[v-dirichards]

@AaronMaxwell

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

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[AaronMaxwell]

#sign-off