fix: pass -Scope correctly when Target=CurrentUser for PowerShellGet package (#167)

## What this changes

Fixes a variable reference bug in PSDepend/PSDependScripts/Package.ps1
where the elseif condition checked $Scope (undefined at that point)
instead of $Dependency.Target. As a result, -Scope was never passed to
Install-Package when Target = 'CurrentUser', causing an elevation
prompt. The Target→Scope logic has been restructured to match the
pattern used in PSGalleryModule.ps1.

## Why

When invoking PSDepend with -Target CurrentUser for PowerShellGet
packages, users were unexpectedly prompted for elevation because the
scope was never set.

Closes #130 

## Type of change

- [X] Bug fix (non-breaking change that corrects incorrect behavior)
- [ ] New feature (non-breaking change that adds functionality)
- [ ] Breaking change (fix or feature that changes existing behavior)
- [ ] Chore / refactor / documentation (no behavior change)

## Checklist

- [ ] Pester tests added or updated to cover the change
- [X] `Invoke-psake Analyze` passes locally with no new warnings
- [X] `Invoke-psake Test` passes locally on at least one platform
- [ ] `CHANGELOG.md` updated (required for any user-facing change)
- [ ] Documentation updated if behavior changed

## Additional notes

The fix mirrors the existing logic in PSGalleryModule.ps1 which handles
the same Target→Scope mapping correctly.

---------

Co-authored-by: Gilbert Sanchez <me@gilbertsanchez.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: Marcel Dutt <41046352+sit-md@users.noreply.github.com>
Co-authored-by: Maarten Piederiet <mpiederiet@users.noreply.github.com>

Author: 5 people

PSDepend/PSDependScripts/Package.ps1

@@ -124,11 +124,13 @@ If($ThisProvider -eq 'PowerShellGet')
     if(-not $Dependency.Target)
     {
         $Scope = 'AllUsers'
-        $InstallParam.Add('Scope', $Scope)
     }
-    elseif($ValidScope -contains $Scope)
+    else
     {
         $Scope = $Dependency.Target
+    }
+    if($ValidScope -contains $Scope)
+    {
         $InstallParam.Add('Scope', $Scope)
     }
 }