Spelling correction: "Calulating" -> "Calculating".

This addresses issue 2178.
diff --git a/app/summerofcode/views/duplicates.py b/app/summerofcode/views/duplicates.py
index c848d24..b862b35 100644
--- a/app/summerofcode/views/duplicates.py
+++ b/app/summerofcode/views/duplicates.py
@@ -43,7 +43,7 @@
 from summerofcode.views.helper import urls as soc_urls
 
 
-_CALCULATING_STATE = translation.ugettext('Calulating')
+_CALCULATING_STATE = translation.ugettext('Calculating')
 _COMPLETED_STATE = translation.ugettext('Completed')
 _NOT_STARTED_STATE = translation.ugettext('Not started')
 _UNKNOWN_STATE = translation.ugettext('Unknown')