exercises(meetup): sync metadata

Reflect the upstream change [1].

[1] exercism/problem-specifications@deae105ba9a1

exercises/practice/meetup/.meta/config.json

@@ -14,6 +14,5 @@
     ]
   },
   "blurb": "Calculate the date of meetups.",
-  "source": "Jeremy Hinegardner mentioned a Boulder meetup that happens on the Wednesteenth of every month",
-  "source_url": "http://www.copiousfreetime.org/"
+  "source": "Jeremy Hinegardner mentioned a Boulder meetup that happens on the Wednesteenth of every month"
 }