Bump MudBlazor from 6.20.0 to 7.15.0

Bumps [MudBlazor](https://github.com/MudBlazor/MudBlazor) from 6.20.0 to 7.15.0.
- [Release notes](https://github.com/MudBlazor/MudBlazor/releases)
- [Changelog](https://github.com/MudBlazor/MudBlazor/blob/dev/CHANGELOG.md)
- [Commits](MudBlazor/MudBlazor@v6.20.0...v7.15.0)

---
updated-dependencies:
- dependency-name: MudBlazor
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Directory.Packages.props

@@ -14,7 +14,7 @@
     <PackageVersion Include="Akka.Streams.TestKit" Version="1.5.20" />
     <PackageVersion Include="Grpc.Tools" Version="2.67.0" />
     <PackageVersion Include="Microsoft.EntityFrameworkCore.SqlServer" Version="8.0.10" />
-    <PackageVersion Include="MudBlazor" Version="6.20.0" />
+    <PackageVersion Include="MudBlazor" Version="7.15.0" />
   </ItemGroup>
   <!-- ASP.NET Package Versions -->
   <ItemGroup>