build: disable rule avoid_classes_with_only_static_members

[dkrutskikh]

What is the purpose of this pull request? (put an "X" next to an item)

[ ] Documentation update
[ ] Bug fix
[ ] New rule
[ ] Changes an existing rule
[ ] Add autofixing to a rule
[ ] Add a CLI option
[ ] Add something to the core
[x] Other, please explain: disable rule avoid_classes_with_only_static_members

What changes did you make? (Give an overview)

Is there anything you'd like reviewers to focus on?

[codecov-commenter]

Codecov Report

Merging #413 (1b322c5) into master (bc56884) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #413   +/-   ##
=======================================
  Coverage   81.04%   81.04%           
=======================================
  Files         166      166           
  Lines        3766     3766           
=======================================
  Hits         3052     3052           
  Misses        714      714           

Impacted Files	Coverage Δ
...s_list/member_ordering_extended/config_parser.dart	100.00% <ø> (ø)

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