update PublishChangeEdit: notify param

[banksean]

This fixes a 400 I was getting when calling PublishChangeEdit on chromium-review.googlesource.com. It told me it expected a json body, so this adds one.

[codecov-io]

Codecov Report

Merging #31 into master will decrease coverage by 0.02%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master      #31      +/-   ##
==========================================
- Coverage   17.32%   17.29%   -0.03%     
==========================================
  Files          20       20              
  Lines        1709     1711       +2     
==========================================
  Hits          296      296              
- Misses       1386     1388       +2     
  Partials       27       27

Impacted Files	Coverage Δ
changes_edit.go	0% <0%> (ø)	⬆️

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[banksean]

The coverage reports confuse me. I don't think I changed the lines it's highlighting in this PR.

[andygrunwald]

Thanks a lot!