exercises(hello-world, leap): sync metadata

Reflect some upstream changes [1][2].

[1] exercism/problem-specifications@ceead5563ebc
[2] exercism/problem-specifications@1904c9bb0ff2

exercises/practice/hello-world/.meta/config.json

@@ -13,7 +13,7 @@
       ".meta/example.zig"
     ]
   },
-  "blurb": "The classical introductory exercise. Just say \"Hello, World!\".",
+  "blurb": "Exercism's classic introductory exercise. Just say \"Hello, World!\".",
   "source": "This is an exercise to introduce users to using Exercism",
   "source_url": "https://en.wikipedia.org/wiki/%22Hello,_world!%22_program"
 }

exercises/practice/leap/.meta/config.json

@@ -13,7 +13,7 @@
       ".meta/example.zig"
     ]
   },
-  "blurb": "Given a year, report if it is a leap year.",
+  "blurb": "Determine whether a given year is a leap year.",
   "source": "CodeRanch Cattle Drive, Assignment 3",
   "source_url": "https://coderanch.com/t/718816/Leap"
 }