chore: revert rollup commonjs plugin to v20

[dnalborczyk]

This PR contains:

• bugfix
• feature
• refactor
• documentation
• other

Are tests included?

• yes (bugfixes and features will not be merged without tests)
• no

Breaking Changes?

• yes (breaking changes will not be merged unless absolutely necessary)
• no

List any relevant issue numbers:

Description

temporary "fixes": #4300 (comment)

/cc @kzc

[codecov]

Codecov Report

Merging #4308 (ce1c8fb) into master (28cc198) will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4308      +/-   ##
==========================================
- Coverage   98.45%   98.42%   -0.03%     
==========================================
  Files         205      205              
  Lines        7311     7313       +2     
  Branches     2082     2083       +1     
==========================================
  Hits         7198     7198              
- Misses         55       56       +1     
- Partials       58       59       +1     

Impacted Files	Coverage Δ
src/watch/fsevents-importer.ts	50.00% <0.00%> (-25.00%)	⬇️

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[kzc]

A mocha test should be added to confirm the existence of the functions in #4300 (comment).

[kzc]

Although this PR would avoid random watch test failures on Mac, it appears that the problem is more nuanced than I first thought - see #4300 (comment).

[dnalborczyk]

superseded by: #4312