fix(typescript-estree): handle optional computed prop w/o type

[bradzacher]

Fixes #1019

[typescript-eslint]

Thanks for the PR, @bradzacher!

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[codecov]

Codecov Report

Merging #1026 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1026      +/-   ##
==========================================
+ Coverage   94.14%   94.14%   +<.01%     
==========================================
  Files         115      115              
  Lines        5019     5020       +1     
  Branches     1404     1405       +1     
==========================================
+ Hits         4725     4726       +1     
  Misses        166      166              
  Partials      128      128

Impacted Files	Coverage Δ
packages/typescript-estree/src/convert.ts	98.96% <100%> (ø)	⬆️