auto dependabot: bump @microsoft/msgraph-sdk-core

Bumps [@microsoft/msgraph-sdk-core](https://github.com/microsoftgraph/msgraph-sdk-typescript-core) from 1.0.0-preview.14 to 1.0.0-preview.15.
- [Release notes](https://github.com/microsoftgraph/msgraph-sdk-typescript-core/releases)
- [Changelog](https://github.com/microsoftgraph/msgraph-sdk-typescript-core/blob/main/CHANGELOG.md)
- [Commits](microsoftgraph/msgraph-sdk-typescript-core@v1.0.0-preview.14...v1.0.0-preview.15)

---
updated-dependencies:
- dependency-name: "@microsoft/msgraph-sdk-core"
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Author: dependabot[bot]