Update dependency MediatR to 8.1.0

[mend-for-github-com[bot]]

This PR contains the following updates:

Package	Type	Update	Change
MediatR	nuget	minor	8.0.1 -> 8.1.0

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Release Notes

jbogard/MediatR (MediatR)

### [`v8.0.2`](https://redirect.github.com/jbogard/MediatR/releases/tag/v8.0.2): 8.0.2 This is a minor release to add support for nullable reference types and target `netstandard2.1` ([#​518](https://redirect.github.com/jbogard/MediatR/issues/518)).

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Configuration

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