fix(eslint-plugin): [no-unnec-type-assertion] allow const assertions

[a-tarasyuk]

Fixes #1734

[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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[a-tarasyuk]

@bradzacher It seems that CI doesn't work :(.

[bradzacher]

hmm. I saw this on another PR but I wasn't sure if it was the PR or what.
It looks like they're just not getting triggered... I'll take a look

[a-tarasyuk]

@bradzacher thanks

[codecov]

Codecov Report

Merging #1741 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1741   +/-   ##
=======================================
  Coverage   95.19%   95.19%           
=======================================
  Files         148      148           
  Lines        6968     6971    +3     
  Branches     2009     2010    +1     
=======================================
+ Hits         6633     6636    +3     
  Misses        124      124           
  Partials      211      211           

Flag	Coverage Δ
#unittest	95.19% <100.00%> (+<0.01%)	⬆️

Impacted Files	Coverage Δ
...-plugin/src/rules/no-unnecessary-type-assertion.ts	97.10% <100.00%> (+0.13%)	⬆️

[bradzacher]

lgtm - thanks for this