refactor: consolidate ADMX policies into main WAU.admx

Remove the separate WAU-Notifier.admx/adml files. All three deadline
policies (UpdateDeadlineDays, ReminderIntervalDays, CompanyName) are
already defined in the main WAU.admx/adml with identical valueName
and registry key paths.

Per Romanitho's feedback on PR #1132: a single ADMX file is easier
to manage in Intune and the GitHub Actions release workflow.

Also fixes a stale comment referencing info.png (now notify_icon.png).

Author: rtylerdavis

Sources/Policies/ADMX/WAU-Notifier.admx

@@ -289,7 +289,7 @@ else {
     $instructionTxt.Text = "Check the box next to apps you're ready to update now, or update all at once. If you don't update all apps now, you will be reminded in $reminderDays $dayLabel."
 }
 
-# Set window icon from WAU's info.png if available
+# Set window icon from WAU's notify_icon.png if available
 $iconPath = Join-Path $PSScriptRoot 'icons\notify_icon.png'
 if (Test-Path $iconPath) {
     $bitmap = New-Object System.Windows.Media.Imaging.BitmapImage