Update ownership of dotnet tutorials

[meaghanlewis]

Summary

This pull request updates the ownership assignments for the docs/core/tutorials section in both the .github/CODEOWNERS file and the docfx.json configuration. The main goal is to reflect new maintainers for these documentation files.

Ownership updates:

• Changed the code owner for docs/core/tutorials/ in .github/CODEOWNERS from @BillWagner to @meaghanlewis.
• Updated the maintainer for docs/core/tutorials/**/**.md in docfx.json from billwagner to meaghanlewis.
• Updated the maintainer for docs/core/tutorials/**/**.md in another section of docfx.json from wiwagn to mosagie.

[BillWagner]

This LGTM. Let's

[meaghanlewis]

Thanks @BillWagner!