Changed prerequisites and practices

Author: marcelweikum

config.json

@@ -1250,16 +1250,14 @@
         "name": "Affine Cipher",
         "uuid": "61374c16-0a99-4616-9244-a38919eafbe1",
         "practices": [
-          "auto",
-          "literals"
+          "math",
+          "exceptions"
         ],
         "prerequisites": [
-          "includes",
-          "namespaces",
-          "if-statements",
-          "booleans",
-          "headers",
-          "comparisons"
+          "functions",
+          "comparisons",
+          "loops",
+          "booleans"
         ],
         "difficulty": 6
       }