chore!: remove support for the legacy notarization tool

[erikian]

• I have read the contribution documentation for this project.
• I agree to follow the code of conduct that this project follows, as appropriate.
• The changes are appropriately documented (if applicable).
• The changes have sufficient test coverage (if applicable).
• The testsuite passes successfully on my local machine (if applicable).

Summarize your changes:

BREAKING CHANGE: remove support for the tool option in osxNotarize, meaning notaryTool will always be used and users will no longer be able to provide tool: 'legacy' (see electron/notarize#141). This also removes the NotarizeLegacyOptions and OsxNotarizeOptions types because they're no longer necessary.

[codecov]

Codecov Report

Merging #1597 (9778540) into main (e34d56c) will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1597      +/-   ##
==========================================
- Coverage   95.66%   95.65%   -0.02%     
==========================================
  Files          15       15              
  Lines         785      783       -2     
==========================================
- Hits          751      749       -2     
  Misses         34       34              

Files	Coverage Δ
src/mac.js	100.00% <ø> (ø)

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[continuous-auth]

🎉 This PR is included in version 18.0.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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