refactor!: only support winston3

[ofrobots]

BREAKING CHANGE: Drop support for winston2 as a semver major change.

Ref: #278

[ofrobots]

This unblocks #278. We may spin off winston2 support (if it is still necessary) into a separate package, or continue to support it from the penultimate semver major branch.

[codecov]

Codecov Report

Merging #297 into master will increase coverage by 1.87%.
The diff coverage is 80%.

@@            Coverage Diff             @@
##           master     #297      +/-   ##
==========================================
+ Coverage    92.3%   94.18%   +1.87%     
==========================================
  Files           6        4       -2     
  Lines         104       86      -18     
  Branches       18       15       -3     
==========================================
- Hits           96       81      -15     
+ Misses          4        2       -2     
+ Partials        4        3       -1

Impacted Files	Coverage Δ
src/index.ts	81.81% <80%> (-3.9%)	⬇️

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[soldair]

looks good. i was confused by how many install tests were left that only changed winston2 to 3 but had the same ts source. but it makes sense because we made it comptable with both tests cases for winston 2 are important for either version.

[DominicKramer]

I also don't have a problem dropping support for Winston 2 with the model of supporting in the future in a separate module or other mechanisms if there is customer need.

[ofrobots]

@JustinBeckwith this is good to land, but an Administrator will have to force land this. Snyk is complaining about the removal of a package.json file. This is intentional.