fix(scope-manager): fix visiting TSAsExpression in assignment

[yeonjuan]

fixes #3336

[typescript-eslint]

Thanks for the PR, @yeonjuan!

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!

---

🙏 Please, if you or your company is finding typescript-eslint valuable, help us sustain the project by sponsoring it transparently on https://opencollective.com/typescript-eslint. As a thank you, your profile/company logo will be added to our main README which receives thousands of unique visitors per day.

[codecov]

Codecov Report

Merging #3355 (62d37c2) into master (ddfab95) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #3355   +/-   ##
=======================================
  Coverage   92.85%   92.85%           
=======================================
  Files         318      318           
  Lines       11048    11048           
  Branches     3128     3128           
=======================================
  Hits        10259    10259           
  Misses        352      352           
  Partials      437      437           

Flag	Coverage Δ
unittest	92.85% <100.00%> (ø)

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

Impacted Files	Coverage Δ
...ackages/scope-manager/src/referencer/Referencer.ts	93.90% <100.00%> (ø)

[bradzacher]

nice catch!
thanks for this!