Yandex engine will return parsing error instead of informing that a CAPTCHA was found. It is confusing for the admin and the users (#5415).
This patch fixes an issue where the CAPTCHA response from Yandex wouldn't be detected, resulting in `ParserError` when trying to parse the response to DOM.
In this fix, I replaced the url condition and instead is checking if the `x-yandex-captcha` header is set, and is equal to `captcha`.
Alternatively, maybe something like `resp.headers.get('Location', '').startswith("https://yandex.com/showcaptcha")` could be done instead. Lastly, setting `params['allow_redirects'] = True` can also work, but this will waste an extra request. Just let me know.
Closes: https://github.com/searxng/searxng/issues/5415
The language_support variable is set to True by default,
and set to False in only 5 engines.
Except the documentation and the /config URL, this variable is not used.
This commit remove the variable definition in the engines, and
set value according to supported_languages length: False when the length is 0,
True otherwise.
Close#2485
