Fix typo in contributors link

Author: mwcraig

CONTRIBUTORS.md

@@ -32,7 +32,7 @@ We are certain the list is incomplete; please let one of us know by opening an [
 + Brian Su ([@brianbbsu](https://github.com/brianbbsu))
 + [@0dminnimda](https://github.com/0dminnimda)
 + Mike Miller ([@Axe319](https://github.com/axe319))
-+ Dan Miller ([@danx0r(https://github.com/danx0r))
++ Dan Miller ([@danx0r](https://github.com/danx0r))
 + Alex Herrera ([@aherrera1721](https://github.com/aherrera1721))
 
 ## Full timeline of vpython development