refactor: cleanup anti-patterns documentation

[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
[ ] Other, please explain:

What changes did you make? (Give an overview)

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

[codecov]

Codecov Report

Merging #548 (92f8e79) into master (b3d2806) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #548   +/-   ##
=======================================
  Coverage   84.97%   84.97%           
=======================================
  Files         219      219           
  Lines        4474     4474           
=======================================
  Hits         3802     3802           
  Misses        672      672           

Impacted Files	Coverage Δ
.../anti_patterns/anti_patterns_list/long_method.dart	100.00% <ø> (ø)
...tterns/anti_patterns_list/long_parameter_list.dart	100.00% <ø> (ø)
...er/anti_patterns/models/pattern_documentation.dart	100.00% <100.00%> (ø)

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