(CAT-1669) - Add trailing comma to completion item

[jordanbreen28]

Summary

Prior to this PR, we would return completion items without a trailing comma. A trailing comma is the suggested style as per the puppet code docs, so we should append this to the returned value.

Additional Context

Add any additional context about the problem here.

• [ ] Root cause and the steps to reproduce. (If applicable)
• [ ] Thought process behind the implementation.

Related Issues (if any)

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Checklist

• [ ] 🟢 Spec tests.
• [ ] 🟢 Acceptance tests.
• [ ] Manually verified.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 11.69%. Comparing base (ad6f043) to head (25660f1).

Files	Patch %	Lines
...pet-languageserver/manifest/completion_provider.rb	0.00%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #372 +/- ## ======================================= Coverage 11.69% 11.69% ======================================= Files 92 92 Lines 11499 11499 ======================================= Hits 1345 1345 Misses 10154 10154 ```

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