[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/webapp.py

@@ -1048,6 +1048,7 @@ def preferences():
             # even if there is no exception
             reliablity = 0
         else:
+            # pylint: disable=consider-using-generator
             reliablity = 100 - sum([error['percentage'] for error in errors if not error.get('secondary')])
 
         reliabilities[e.name] = {