feat: when cancelling OS upgrade, delete any plugin files that were d… (#1823)

…ownloaded as part of the upgrade

<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit

* **Bug Fixes**
* Improved cleanup of temporary plugin configuration files during update
cancellation operations.

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settings.</sub>

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plugin/source/dynamix.unraid.net/usr/local/emhttp/plugins/dynamix.plugin.manager/include/UnraidUpdateCancel.php

@@ -46,6 +46,11 @@ class UnraidUpdateCancel
       $readmeContent .= "Unraid OS by [Lime Technology, Inc.](https://lime-technology.com).\n";
       file_put_contents($readmeFile, $readmeContent);
 
+      // Delete plugin files that were downloaded during the OS upgrade
+      if (is_dir("/boot/config/plugins-nextboot")) {
+        shell_exec("rm -rf /boot/config/plugins-nextboot");
+      }
+
       return ['success' => true]; // Upgrade handled successfully
     } catch (\Throwable $th) {
       return [