[CONFIG] Update CODEOWNERS (#104)

Updating stale codeowners file to reflect current maintainers

Author: michael-linnane-lrn

.github/CODEOWNERS

@@ -1,3 +1,3 @@
 # These owners will be the default owners for everything in
 # the repo. Unless a later match takes precedence,
-*       @michael-linnane-lrn @ferdia-sopermaccafraidh-lrn
+*       @michael-linnane-lrn @sean-roche-lrn @jack-oconnor-lrn