Update instructions.md

Change camelCase to snake_case for function name

exercises/concept/gotta-snatch-em-all/.docs/instructions.md

@@ -56,10 +56,10 @@ boring_cards([set.from_list(["Scientuna"]), set.from_list(["Newthree", "Scientun
 
 Do you and your friends collectively own all of the Blorkemon™️ cards?
 
-Implement `totalCards`, which takes a list of collections and returns the total number of different cards in all of the collections.
+Implement `total_cards`, which takes a list of collections and returns the total number of different cards in all of the collections.
 
 ```gleam
-totalCards [set.from_list(["Scientuna"]), set.from_list(["Newthree", "Scientuna"])]
+total_cards [set.from_list(["Scientuna"]), set.from_list(["Newthree", "Scientuna"])]
 // -> 2
 ```