Under /etc/yum.repos.d, there should be a file governing the yum setup of the development repo. Find the one you've enabled, open it up (as root) in a text editor and switch "enabled=1" to "enabled=0".
Depending on how many packages you've got from the development repo, you may have somewhat busted your system.
"What is freedom? To have the will to be responsible for one's self." - Stirner