fix(eslint-plugin): [no-unnecessary-condition] fix autofixer for computed properties

[a-tarasyuk]

Fixes #1658

[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 #1662 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1662      +/-   ##
==========================================
+ Coverage   95.35%   95.37%   +0.02%     
==========================================
  Files         145      146       +1     
  Lines        6804     6836      +32     
  Branches     1958     1965       +7     
==========================================
+ Hits         6488     6520      +32     
  Misses        111      111              
  Partials      205      205

Impacted Files	Coverage Δ
...eslint-plugin/src/rules/no-unsafe-member-access.ts	100% <100%> (ø)
packages/eslint-plugin/src/util/types.ts	81.3% <100%> (+0.35%)	⬆️
packages/eslint-plugin/src/util/astUtils.ts	73.68% <100%> (+1.46%)	⬆️

[bradzacher]

LGTM - thanks for fixing this.