fix(eslint-plugin): [array-type] parenthesize ReadonlyArray fix

[a-tarasyuk]

Fixes #2741

[typescript-eslint]

Thanks for the PR, @a-tarasyuk!

typescript-eslint is a 100% community driven project, and we are incredibly grateful that you are contributing to that community.

The core maintainers work on this in their personal time, so please understand that it may not be possible for them to review your work immediately.

Thanks again!

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[codecov]

Codecov Report

Merging #2747 (56384b5) into master (e82698c) will decrease coverage by 0.00%.
The diff coverage is 80.00%.

@@            Coverage Diff             @@
##           master    #2747      +/-   ##
==========================================
- Coverage   92.79%   92.79%   -0.01%     
==========================================
  Files         297      297              
  Lines        9833     9835       +2     
  Branches     2762     2764       +2     
==========================================
+ Hits         9125     9126       +1     
  Misses        332      332              
- Partials      376      377       +1     

Flag	Coverage Δ
unittest	92.79% <80.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
packages/eslint-plugin/src/rules/array-type.ts	97.33% <80.00%> (-1.30%)	⬇️

[bradzacher]

LGTM - thanks for this