Kernel: Add missing include to Jail.h

Author: https://github.com/mrkct
Commit: d0403d24d4
Pull-request: https://github.com/SerenityOS/serenity/pull/17887
Reviewed-by: https://github.com/Hendiadyoin1
Reviewed-by: https://github.com/Ollrogge
Reviewed-by: https://github.com/Panky-codes
Reviewed-by: https://github.com/nico
Reviewed-by: https://github.com/supercomputer7

Kernel/Jail.h

@@ -17,6 +17,7 @@
 #include <Kernel/KString.h>
 #include <Kernel/Library/LockRefPtr.h>
 #include <Kernel/Locking/SpinlockProtected.h>
+#include <Kernel/Process.h>
 
 namespace Kernel {