## Summary
- Restore the generated .NET SDK project target framework from `net8.0`
to `net6.0`.
- Keep the change scoped to the framework bump introduced by #857.
## Testing
- `dotnet build sdk/dotnet/Pulumi.DockerBuild.csproj --source
https://api.nuget.org/v3/index.json`
Note: a plain `dotnet build sdk/dotnet/Pulumi.DockerBuild.csproj` first
failed during restore because user-level NuGet sources point at missing
local worktree paths. The command above restricts restore to nuget.org;
the SDK build also needs the transient `sdk/dotnet/version.txt` that the
repo's `sdk/dotnet` generation target creates before building.
Co-authored-by: Codex <codex@openai.com>
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