🪲 [Fix]: Update Get-GitHubAppInstallableOrganization to handle array of objects (#404)

## Description

This pull request includes a small change to the
`Get-GitHubAppInstallableOrganization.ps1` function. The change modifies
how the `Response` object is processed, ensuring that each item in the
response is properly converted into a `GitHubOrganization` object.

## Type of change

<!-- Use the check-boxes [x] on the options that are relevant. -->

- [ ] 📖 [Docs]
- [x] 🪲 [Fix]
- [ ] 🩹 [Patch]
- [ ] ⚠️ [Security fix]
- [ ] 🚀 [Feature]
- [ ] 🌟 [Breaking change]

## Checklist

<!-- Use the check-boxes [x] on the options that are relevant. -->

- [x] I have performed a self-review of my own code
- [x] I have commented my code, particularly in hard-to-understand areas

Author: MariusStorhaug

src/functions/private/Apps/GitHub Apps/Get-GitHubAppInstallableOrganization.ps1

@@ -47,7 +47,7 @@
         }
 
         Invoke-GitHubAPI @inputObject | ForEach-Object {
-            [GitHubOrganization]::new($_.Response)
+            $_.Response | ForEach-Object { [GitHubOrganization]::new($_) }
         }
     }