feat(experimental-utils): update eslint types to match v6.8

[bradzacher]

went through the history on the definitely typed types to update our copies.
I need to pay a bit more attention to ESLint releases so that I don't miss this stuff.

[typescript-eslint]

Thanks for the PR, @bradzacher!

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 #1846 into master will not change coverage by %.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1846   +/-   ##
=======================================
  Coverage   94.71%   94.71%           
=======================================
  Files         161      161           
  Lines        7338     7338           
  Branches     2101     2101           
=======================================
  Hits         6950     6950           
  Misses        165      165           
  Partials      223      223           

Flag	Coverage Δ
#unittest	94.71% <ø> (ø)

Impacted Files	Coverage Δ
...rimental-utils/src/ts-eslint-scope/ScopeManager.ts	100.00% <ø> (ø)
.../experimental-utils/src/ts-eslint-scope/analyze.ts	100.00% <ø> (ø)
...ages/experimental-utils/src/ts-eslint/CLIEngine.ts	0.00% <ø> (ø)
...ackages/experimental-utils/src/ts-eslint/Linter.ts	100.00% <ø> (ø)
...ges/experimental-utils/src/ts-eslint/RuleTester.ts	28.57% <ø> (ø)