tests: test_gen_menu: Remove app_context initialisation
tests: test_gen_menu: Remove app_context initialisation

This is no longer required since the global object "Flask.g.db" is no
longer coupled to the gen_menu module.

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