OSIS-1744 Fixed typo
OSIS-1744 Fixed typo

	modified:   base/models/prerequisite.py

uclouvain/osis_louvain,uclouvain/OSIS-Louvain,uclouvain/osis,uclouvain/OSIS-Louvain,uclouvain/osis_louvain,uclouvain/OSIS-Louvain,uclouvain/osis,uclouvain/osis,uclouvain/osis_louvain,uclouvain/osis