fix: add [OutputType] to scaffold function (PSUseOutputTypeCorrectly)

The scaffold Get-PSModuleTest function output a string but was missing the
[OutputType([string])] attribute. This triggered a PSScriptAnalyzer
PSUseOutputTypeCorrectly failure when README.md changes caused
HasImportantChanges to be true and the full lint suite ran.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: MariusStorhaug

src/functions/public/Get-PSModuleTest.ps1

@@ -11,6 +11,7 @@ function Get-PSModuleTest {
 
         "Hello, World!"
     #>
+    [OutputType([string])]
     [CmdletBinding()]
     param (
         # Name of the person to greet.