chore: revert "move tasks from prepare to prepublishOnly"

[bajtos]

This reverts commit afac0cf
(pull request #928) as an experimental attempt to fix our failing build.

Checklist

• npm test passes on your machine
• New tests added or existing tests modified to cover all changes
• Code conforms with the style guide
• Related API Documentation was updated
• Affected artifact templates in packages/cli were updated
• Affected example projects in packages/example-* were updated

[virkt25]

Use revert type for commit message instead of chore: revert.
Will review once builds pass.

[bajtos]

For the record, I am experiencing a weird build failure in #933. I thought it was unrelated to those changes, but since #924 is passing the build on Travis CI, I am almost sure the problem is not on master but in my pull request adding microservices example.

I am closing this pull request for now.