[mod] drop fasttext-predict (#5795)

Removes the `fasttext-predict` dependency and the language detection code.

If a user now selects `auto` for the search language, the detected language now
falls back directly to the `Accept-Language` header sent by the browser (which was already the fallback when fasttext returned no result).

- fasttext's [language detection is unreliable](https://github.com/searxng/searxng/issues/4195) for some languages, especially short search queries, and in particular for queries containing proper names which is a common case.
- `fasttext-predict` consumes [significant memory](https://github.com/searxng/searxng/pull/1969#issuecomment-1345366676) without offering users much real value.
- the upstream fasttext project was archived by Meta in 2024
- users already have two better alternatives: the `Accept-Language` header and the search-syntax language prefix (e.g. `:fr` or `:de`).

Related: https://github.com/searxng/searxng/issues/4195
Closes: https://github.com/searxng/searxng/issues/5790

searxng_extra/update/update_engine_descriptions.py

@@ -19,7 +19,7 @@ from searx.engines import wikidata, set_loggers
 from searx.utils import extract_text, searxng_useragent
 from searx.locales import LOCALE_NAMES, locales_initialize, match_locale
 from searx import searx_dir
-from searx.utils import gen_useragent, detect_language
+from searx.utils import gen_useragent
 import searx.search
 import searx.network
 from searx.data import data_dir
@@ -169,7 +169,7 @@ def get_website_description(url, lang1, lang2=None):
     lang = extract_text(html.xpath('/html/@lang'))
     if lang is None and len(lang1) > 0:
         lang = lang1
-    lang = detect_language(description) or lang or 'en'
+    lang = lang or 'en'
     lang = lang.split('_')[0]
     lang = lang.split('-')[0]
     return (lang, description)