context_spec: fix ActiveRecord conditionals in test
context_spec: fix ActiveRecord conditionals in test

for #join_sources.

vaski/ransack,Mario245/ransack,activerecord-hackery/ransack,nagyt234/ransack,martndemus/ransack,roman-franko/ransack,mariorcardoso/ransack,avit/ransack,laserlemon/ransack,Eric-Guo/ransack,reinteractive/ransack,amboxer21/ransack,outstand/ransack,johan--/ransack,AndrewSwerlick/ransack,guilleva/ransack