fix broken links in challenge coins page (#739)

Author: thisisharsh7

content/contributing/challenge-coins/contents.lr

@@ -44,16 +44,15 @@ Coin.</em></figcaption>
 </figure>
 
 The first run of 100 BeeWare Challenge Coins were commissioned thanks to
-financial support from [MaxCDN](/community/members/maxcdn/). They also
-wrote an [article about
+financial support from MaxCDN. They also wrote an [article about
 BeeWare](https://web.archive.org/web/20170923205703/https://www.maxcdn.com/blog/beeware-be-sticky/)
 on their blog.
 
-[Revolution Systems](/community/members/revsys/) provided the funding
-for the second pressing of the BeeWare challenge coins.
+Revolution Systems provided the funding for the second pressing of the
+BeeWare challenge coins.
 
-[GitHub](/community/members/github/) provided the funding for the first
-pressing of the BeeWare Yak Herder challenge coins.
+GitHub provided the funding for the first pressing of the BeeWare Yak
+Herder challenge coins.
 
 <figure>
 <img src="/contributing/challenge-coins/sprint-coin.jpg"