Build pipeline: PrintGitInformationModule always prints 'Git Info: {}'

[thomhurst]

Category: dogfood output — Breaking: no

src/ModularPipelines.Build/Modules/PrintGitInformationModule.cs:14 serializes context.Git().Information, but GitInformation exposes only methods (GetInfoAsync(), Commits(...)) and no serializable properties, so the JSON is always {} (visible in every run's PrintGitInformationModule group).

Fix: serialize await context.Git().Information.GetInfoAsync() instead. Worth fixing — this module is showcase output in the project's own pipeline.

Part of #3239 (round 2 addendum).