remove dead TARGETS code

rainboard/utils.py

@@ -9,7 +9,6 @@ from django.utils.safestring import mark_safe
 logger = logging.getLogger('rainboard.utils')
 
 SOURCES = IntEnum('Sources', 'github gitlab redmine robotpkg travis')
-TARGETS = IntEnum('Targets', '14.04 16.04 17.10 18.04 dubnium jessie erbium stretch 20.04')
 INVALID_MAILS = ('localhost', 'none', 'noreply', 'example')