Fix already-passing koans

src/koans/maps.clj

@@ -1,6 +1,6 @@
 (meditations
   "There are two ways to create maps"
-  (= {} (hash-map))
+  (= __ (hash-map))
 
   "Maps in clojure associate keys with values"
   (= __ (count (hash-map)))

src/koans/sets.clj

@@ -1,6 +1,6 @@
 (meditations
   "You can create a set in two ways"
-  (= #{} (set nil))
+  (= #{} (set __))
 
   "They are another important data structure in clojure"
   (= __ (count #{1 2 3}))