Update AdjustTokenPrivileges PInvoke usage

Refactored the AdjustTokenPrivileges call to use null for the previous state and an out variable for the return length, improving compatibility with the PInvoke signature and aligning with recommended usage.

Author: Jack251970

Plugins/Flow.Launcher.Plugin.Sys/Main.cs

@@ -175,7 +175,7 @@ private static unsafe bool EnableShutdownPrivilege()
                     Privileges = new() { e0 = new LUID_AND_ATTRIBUTES { Luid = luid, Attributes = TOKEN_PRIVILEGES_ATTRIBUTES.SE_PRIVILEGE_ENABLED } }
                 };
 
-                if (!PInvoke.AdjustTokenPrivileges(tokenHandle, false, &privileges, 0, null, null))
+                if (!PInvoke.AdjustTokenPrivileges(tokenHandle, false, &privileges, null, out var _))
                 {
                     return false;
                 }