Bug 55118: use the family name and site code to get sources

instead of the language code only
This prevents the script from importing a source for xxwiki
for data imported from xxwikivoyage or xxwikisource (bug 62037)

Change-Id: I29df011b82fd8687d4c38def62d0c0ea3a1b7994
Merge "Bug 55118: use the family name and site code to get sources"