[fix] make test.robot: firefox profile: intl.accept_languages=en

make sure Firefox in test.robot asks for English pages

searx/testing.py

@@ -79,7 +79,7 @@ class SearxRobotLayer():
 def run_robot_tests(tests):
     print('Running {0} tests'.format(len(tests)))
     for test in tests:
-        with Browser('firefox', headless=True) as browser:
+        with Browser('firefox', headless=True, profile_preferences={'intl.accept_languages': 'en'}) as browser:
             test(browser)