fix(eslint-plugin): isTypeReadonly error with <TS3.7

[RebeccaStevens]

No description provided.

[typescript-eslint]

Thanks for the PR, @RebeccaStevens!

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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[nx-cloud]

Nx Cloud Report

CI ran the following commands for commit a6c3bad. Click to see the status, the terminal output, and the build insights.

📂 See all runs for this branch

Status	Command
	nx test @typescript-eslint/eslint-plugin-tslint
	nx test @typescript-eslint/eslint-plugin
	nx test @typescript-eslint/eslint-plugin-internal
	nx test @typescript-eslint/eslint-plugin-tslint
	nx test @typescript-eslint/eslint-plugin
	nx test @typescript-eslint/eslint-plugin-tslint
	nx test @typescript-eslint/eslint-plugin
	nx run-many --target=typecheck --all --parallel
	nx run-many --target=build --all --parallel
	nx test @typescript-eslint/parser
	nx test @typescript-eslint/experimental-utils
	nx test @typescript-eslint/scope-manager

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[codecov]

Codecov Report

Merging #3731 (8727289) into master (db78642) will increase coverage by 0.86%.
The diff coverage is 33.33%.

❗ Current head 8727289 differs from pull request most recent head a6c3bad. Consider uploading reports for the commit a6c3bad to get more accurate results

@@            Coverage Diff             @@
##           master    #3731      +/-   ##
==========================================
+ Coverage   92.68%   93.55%   +0.86%     
==========================================
  Files         327      147     -180     
  Lines       11351     7866    -3485     
  Branches     3201     2492     -709     
==========================================
- Hits        10521     7359    -3162     
+ Misses        369      162     -207     
+ Partials      461      345     -116     

Flag	Coverage Δ
unittest	93.55% <33.33%> (+0.86%)	⬆️

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

Impacted Files	Coverage Δ
packages/eslint-plugin/src/util/isTypeReadonly.ts	94.20% <33.33%> (-2.82%)	⬇️
...rimental-utils/src/ts-eslint-scope/ScopeManager.ts
...es/experimental-utils/src/ts-eslint-scope/index.ts
...ges/experimental-utils/src/ast-utils/predicates.ts
packages/scope-manager/src/lib/es2020.promise.ts
packages/experimental-utils/src/json-schema.ts
packages/scope-manager/src/lib/es2018.promise.ts
...mental-utils/src/ts-eslint-scope/PatternVisitor.ts
packages/typescript-estree/src/ast-converter.ts
...escript-estree/src/semantic-or-syntactic-errors.ts
... and 171 more

[bradzacher]

thanks for fixing this!