gnu: hidapi: Fix 'license'.

* gnu/packages/libusb.scm (hidapi)[license]: Actually call
'non-copyleft'.

gnu/packages/libusb.scm

@@ -237,4 +237,4 @@ (define-public hidapi
     ;; HIDAPI can be used under one of three licenses.
     (license (list gpl3
                    bsd-3
-                   non-copyleft "file://LICENSE-orig.txt"))))
+                   (non-copyleft "file://LICENSE-orig.txt")))))