[fix] prepare for pylint 2.14.0

Remove issue reported by Pylint 2.14.0:

- no-self-use: has been moved to optional extension [1]
- The refactoring checker now also raises 'consider-using-generator' messages
  for max(), min() and sum(). [2]

.pylintrc:
  - <option name>-hint has been removed since long, Pylint 2.14.0 raises an
    error on invalid options
  - bad-continuation and bad-whitespace have been removed [3]

[1] https://pylint.pycqa.org/en/latest/whatsnew/2/2.14/summary.html#removed-checkers
[2] https://pylint.pycqa.org/en/latest/whatsnew/2/2.14/full.html#what-s-new-in-pylint-2-14-0
[2] https://pylint.pycqa.org/en/latest/whatsnew/2/2.6/summary.html#summary-release-highlights

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/search/__init__.py

@@ -133,7 +133,7 @@ class Search:
 
     def search_multiple_requests(self, requests):
         # pylint: disable=protected-access
-        search_id = uuid4().__str__()
+        search_id = str(uuid4())
 
         for engine_name, query, request_params in requests:
             th = threading.Thread(  # pylint: disable=invalid-name