cleanup: helm gitignore

[camilamacedo86]

Description of the change:

• For Helm-based Operators, cleanup the file .gitignore in order to not have invalid instructions for the type.

Motivation for the change:

• keep standard across the project
• helm operator has no go files and should not have its instructions in the gitignore as well.

Checklist

If the pull request includes user-facing changes, extra documentation is required:

• Add a new changelog fragment in changelog/fragments (see changelog/fragments/00-template.yaml)
• Add or update relevant sections of the docs website in website/content/en/docs

[joelanford]

/lgtm