Remove templates from the build

[nmuesch]

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• Fill out the template below. Any pull request that does not include enough information to be reviewed in a timely manner may be closed at the maintainers' discretion.
• The pull request must only fix one issue, or add one feature, at the time.

What does this PR do?

This PR stops shipping the template files with the buildpack (and removes them from the gitignore)
Since this PR in the datadog-agent was merged DataDog/datadog-agent#4782, the template files are included in the agent binary directly and aren't needed here anymore.

I've tested a custom buildpack with the latest puppy agent off the master branch, and was able to successfully run the status command.

Review checklist (to be filled by reviewers)

• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have one changelog/ label attached. If applicable it should have the backward-incompatible label attached.
• PR should not have do-not-merge/ label attached.
• If Applicable, issue must have kind/ and severity/ labels attached at least.