Refactor: Improve code clarity and remove unused variable

Renames the event handler parameter from `$sender` to `$eventSource` for better readability.

Removes an unused variable in the parallel processing function to clean up the code.

FFUDevelopment/FFU.Common/FFU.Common.Parallel.psm1

@@ -34,7 +34,6 @@ function Invoke-ParallelProcessing {
     }
     $resultsCollection = [System.Collections.Generic.List[object]]::new()
     $jobs = @()
-    $results = @() # Store results from jobs
     $totalItems = $ItemsToProcess.Count
     $processedCount = 0
 

FFUDevelopment/FFUUI.Core/FFUUI.Core.WindowsSettings.psm1

@@ -540,15 +540,15 @@ function BuildFeaturesGrid {
         $chk.Content = $featureName
         $chk.Margin = "5"
         $chk.Add_Checked({
-            param($sender, $e)
-            $window = [System.Windows.Window]::GetWindow($sender)
+                param($eventSource, $e)
+                $window = [System.Windows.Window]::GetWindow($eventSource)
                 if ($null -ne $window) {
                     UpdateOptionalFeaturesString -State $window.Tag
                 }
             })
         $chk.Add_Unchecked({
-            param($sender, $e)
-            $window = [System.Windows.Window]::GetWindow($sender)
+                param($eventSource, $e)
+                $window = [System.Windows.Window]::GetWindow($eventSource)
                 if ($null -ne $window) {
                     UpdateOptionalFeaturesString -State $window.Tag
                 }