Make copyright hint more specific.

This will help detect SPDX-FileContributor tags
But not plain "contributor" words

Reported-by: Rainer Thieringer @rainerth
Reference: #1816
Signed-off-by: Philippe Ombredanne <pombredanne@nexb.com>

Author: pombredanne

src/cluecode/copyrights_hint.py

@@ -61,7 +61,7 @@
     'right',
     'reserv',
     'auth',
-    'contributor',
+    'filecontributor',
     'devel',
     '<s>',
     '</s>',