Form setting removes the feature when disabled

[lindseymacmillan]

Resolves #4

Description

This PR fixes a bug which prevented changes in the DtD "Enabled/Disabled" form setting from being reflected on the frontend. Previously, the logic used to render the DtD fields was checking for a boolean, when the meta field is instead stored as a string (enabled or disabled).

Affects

This PR affects logic in the DonationForm class, used to determine whether or not the DtD field should be rendered on the frontend.

Pre-review Checklist

• [x] Acceptance criteria satisfied and marked in related issue
• [x] Relevant @since tags included in DocBlocks
• [x] Changes logged to the Unreleased section of CHANGELOG.md
• [x] Self Review of code and UX completed

Testing Instructions

1. Enable the feature on a form and save it. Confirm it shows on the form as intended.
2. Disable the feature on that same form and save.
3. View the form and confirm that the Company Matching field no longer appears on the form.