Add MauiAntGrpcClient to Dependabot configuration

[StephenHidem]

MauiAntGrpClient previously failed dependency scanning. Test this again.

[gemini-code-assist]

Code Review

This pull request updates the Dependabot configuration to include the MauiAntGrpcClient project for automated dependency updates. Feedback indicates that Dependabot may fail to scan this directory because the project targets net10.0 and references package versions not found on the public NuGet gallery, suggesting that a registries section should be added to the configuration to ensure successful scanning.

[gemini-code-assist]

The project MauiAntGrpcClient.csproj references package versions (e.g., Microsoft.Maui.Controls v10.0.51 and Grpc.Net.Client v2.76.0) that are not available on the public NuGet gallery. Dependabot will fail to scan this directory unless it can access the registry where these packages are hosted. If these are from a private or preview feed, you should add a registries section to this configuration file. Additionally, the project targets net10.0, which is likely not yet supported by Dependabot and could be the primary reason for the previous scanning failures mentioned in the PR description.