Update CITATION.md

Author: hossam26644

CITATION.md

@@ -26,4 +26,5 @@ Bibtex record:
   author = {Jerome Kelleher and Yan Wong and Anthony W. Wohns and Chaimaa Fadil and Patrick K. Albers and Gil McVean},
   title = {Inferring whole-genome histories in large population datasets},
   journal = {Nature Genetics}
-}
+}
+```