Don't use cbmc-developers as a code owner

Leave code owners for test folders unspecified

Author: Owen Jones

CODEOWNERS

@@ -45,13 +45,6 @@ src/cpp/ @kroening @tautschnig @peterschrammel
 
 # These files change frequently and changes are low-risk
 
-src/util/irep_ids.def @diffblue/cbmc-developers
-
-unit/ @diffblue/cbmc-developers
-regression/ @diffblue/cbmc-developers
-jbmc/unit/ @diffblue/cbmc-developers
-jbmc/regression/ @diffblue/cbmc-developers
-
 scripts/ @diffblue/devops @thk123 @forejtv @peterschrammel
 .travis.yml @diffblue/devops @thk123 @forejtv @peterschrammel
 appveyor.yml @diffblue/devops @thk123 @forejtv @peterschrammel