Add test for "gen_dropdown_json"
Add test for "gen_dropdown_json"

* wqflask/tests/api/test_gen_menu.py: Add new test

genenetwork/genenetwork2,pjotrp/genenetwork2,zsloan/genenetwork2,genenetwork/genenetwork2,pjotrp/genenetwork2,zsloan/genenetwork2,zsloan/genenetwork2,pjotrp/genenetwork2,genenetwork/genenetwork2,pjotrp/genenetwork2,zsloan/genenetwork2,genenetwork/genenetwork2,pjotrp/genenetwork2