Synced practice exercise metadata. (#3508)

exercises/practice/binary-search-tree/.meta/config.json

@@ -22,6 +22,5 @@
     ]
   },
   "blurb": "Insert and search for numbers in a binary tree.",
-  "source": "Josh Cheek",
-  "source_url": "https://twitter.com/josh_cheek"
+  "source": "Josh Cheek"
 }

exercises/practice/clock/.meta/config.json

@@ -30,6 +30,5 @@
     ]
   },
   "blurb": "Implement a clock that handles times without dates.",
-  "source": "Pairing session with Erin Drummond",
-  "source_url": "https://twitter.com/ebdrummond"
+  "source": "Pairing session with Erin Drummond"
 }

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

@@ -30,5 +30,5 @@
   },
   "blurb": "Calculate the date of meetups.",
   "source": "Jeremy Hinegardner mentioned a Boulder meetup that happens on the Wednesteenth of every month",
-  "source_url": "https://twitter.com/copiousfreetime"
+  "source_url": "http://www.copiousfreetime.org/"
 }