Omit empty fields in CodeBuildPhase

[calavera]

The last element of a list of phases sent by code build only contains start-time and phase-type, the rest of the fields are missing.

I don't know why it only sends those two fields, but I've confirmed this with the CodeBuild folks.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov-commenter]

Codecov Report

Merging #428 (51c8561) into main (e7ef344) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #428   +/-   ##
=======================================
  Coverage   71.66%   71.66%           
=======================================
  Files          19       19           
  Lines        1041     1041           
=======================================
  Hits          746      746           
  Misses        228      228           
  Partials       67       67           

Impacted Files	Coverage Δ
events/codebuild.go	38.46% <ø> (ø)

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[calavera]

@carlzogh I don't have permissions to merge my own PRs here 🤣 do you mind merging this and #427? 🙏