Merge pull request #501 from fanaugen/difference_squares_typo

difference-of-squares: fix typo in blurb

Author: stkent

exercises/difference-of-squares/metadata.yml

@@ -1,4 +1,4 @@
 ---
-blurb: "Find the difference between the sum of the squares and the square of the sums of the first N natural numbers."
+blurb: "Find the difference between the sum of the squares and the square of the sum of the first N natural numbers."
 source: "Problem 6 at Project Euler"
 source_url: "http://projecteuler.net/problem=6"