Fix broken line in leap description (#2121)

I missed another spot in the big one-sentence-per-line overhaul.

Author: kytrinyx

exercises/leap/description.md

@@ -15,10 +15,8 @@ For example, 1997 is not a leap year, but 1996 is.
 
 ## Notes
 
-Though our exercise adopts some very simple rules, there is more to
-learn!
+Though our exercise adopts some very simple rules, there is more to learn!
 
-For a delightful, four minute explanation of the whole leap year
-phenomenon, go watch [this youtube video][video].
+For a delightful, four minute explanation of the whole leap year phenomenon, go watch [this youtube video][video].
 
 [video]: http://www.youtube.com/watch?v=xX96xng7sAE