Drop language parameter from test configuration

tracim/test.ini

 # sqlalchemy.url = mysql+pymysql://tracimuser:tracimpassword@127.0.0.1/tracimdb_test
 sqlalchemy.url = sqlite:///tracimdb_test.sqlite
 use = config:development.ini
-lang = fr
 
 [app:main_without_authn]
 use = main