Change Rest API difficulty from 7 to 8 to be consistent with the 2/5/8 numbering (#103)

Author: IsaacG

config.json

@@ -186,14 +186,6 @@
         "prerequisites": [],
         "difficulty": 5
       },
-      {
-        "slug": "rest-api",
-        "name": "REST API",
-        "uuid": "51275817-1b95-48d9-b7ab-bbbf8720acb7",
-        "practices": [],
-        "prerequisites": [],
-        "difficulty": 7
-      },
       {
         "slug": "acronym",
         "name": "Acronym",
@@ -258,6 +250,14 @@
         "prerequisites": [],
         "difficulty": 8
       },
+      {
+        "slug": "rest-api",
+        "name": "REST API",
+        "uuid": "51275817-1b95-48d9-b7ab-bbbf8720acb7",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 8
+      },
       {
         "slug": "roman-numerals",
         "name": "Roman Numerals",