🤖 Fix invalid UUIDs (#90)

This commit regenerates each UUID that was not a valid version 4 UUID
compliant with RFC 4122 in the canonical textual representation.

Each UUID should match this regular expression:
`^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$`

A track can generate a suitable UUID by running `configlet uuid`.

config.json

@@ -84,7 +84,7 @@
       {
         "slug": "hello-world",
         "name": "Hello World",
-        "uuid": "53156fc9-0945-f080-08a9-ce269bfc9121a5d2c5c",
+        "uuid": "7873ac3b-7f9e-45b3-b509-5a9c7dc84130",
         "practices": [],
         "prerequisites": [],
         "difficulty": 1,