Nit: misleading phrasing when updating packages

When using `aspire update --channel daily` to update a 14.6 project to `13.6.0-preview.1.26410.1+9b79ab510c9f171c48e3af1d69ff6a941127f9a5, the output is a bit misleading

The output says `Added` (past tense) as if it has already added the entries to the file, and then at the end asks for permissions at the end. If you decline the update, then the entries are never added.

The phrasing should use the present tense (`Adding`) or an instruction (i.e. `Add`) because the changes are only proposals, and not actually made until you accept them with the final prompt.

```
Perform updates? [Y/n]: y

Which directory for NuGet.config file? (REDACTED): REDACTED

Added: https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet9/nuget/v3/index.json

Mapping: Aspire* (added)

Added: https://api.nuget.org/v3/index.json

Mapping: * (added)

Retained: REDACTED

Mapping: *

Apply these changes to NuGet.config? [Y/n]: n
```

Start at the `aspire update --channel daily` command and trace where the NuGet.config proposal output is formatted, searching for the `Added:` wording. Verify that the displayed wording describes proposed changes before the final permission prompt, including when the user declines, and check the command's existing tests if available.

Written by the indexing model from the issue text.