fixed $source null check, reference to $Params

$source check causes:
FAILED! => {"changed": false, "failed": true, "msg": "A parameter cannot be found that matches parameter name 'Source'."}

$Params.Remove causes:
FAILED! => {"changed": false, "failed": true, "msg": "Method invocation failed because [System.Management.Automation.PSCustomObject] does not contain a method named 'Remove'."}

lib/ansible/modules/windows/win_feature.ps1

@@ -63,7 +63,7 @@ If ($state -eq "present") {
         $InstallParams.add("IncludeManagementTools",$includemanagementtools)
     }
     
-    if ($source -ne $null)
+    if ($source)
     {
         $InstallParams.add("Source",$source)
     }
@@ -77,7 +77,7 @@ If ($state -eq "present") {
         ElseIf (Get-Command "Add-WindowsFeature" -ErrorAction SilentlyContinue) {
             if ($IncludeManagementTools)
             {
-                $Params.Remove("IncludeManagementTools")
+                $InstallParams.Remove("IncludeManagementTools")
             }
             $featureresult = Add-WindowsFeature @InstallParams
         }