Update arithmetic_slices.py

Author: zirea3l

dynamic_programming/arithmetic_slices.py

@@ -53,7 +53,7 @@ def numberofarithmeticslices(self, nums):
         to check if they form an arithmetic pattern.
 
         So at each step, 
-        we’re looking at a triplet ending at index `i`.
+        we are looking at a triplet ending at index `i`.
         """
 
         return total