Change Feature request template's label from documentation to enhancement

### Overview

We need to change the label applied by the "Feature request" issue template from `documentation` to `enhancement`, because every feature suggestion opened through it is currently filed as documentation work. This makes the `documentation` label useless as a filter and hides real feature requests from anyone browsing by `enhancement`.

### Action Items

- [ ] In `.github/ISSUE_TEMPLATE/feature_request.md`, change the front matter line `labels: documentation` (line 5 at time of writing) to `labels: enhancement`. If the line number has drifted, it is the `labels:` key in the YAML front matter at the top of the file, between `title:` and `assignees:`.
- [ ] **After the PR merges to `main`**, verify: open https://github.com/hackforla/incubator/issues/new/choose, start a "Feature request", and confirm the right-hand Labels box shows `enhancement` and not `documentation`. Close the draft without submitting. This step cannot be done from the PR branch — GitHub serves issue templates from the default branch only, so the change is invisible until it merges. Don't close this issue until you have checked.
- [ ] Leave the rest of the template alone — only the label is in scope.

### Resources/Instructions

- File to edit: https://github.com/hackforla/incubator/blob/main/.github/ISSUE_TEMPLATE/feature_request.md
- Both `documentation` and `enhancement` already exist as labels in this repo, so no label needs creating: https://github.com/hackforla/incubator/labels
- This template is one of the ones being kept, not one of the 15 slated for deletion in #146 — so it is worth fixing rather than removing.

Open .github/ISSUE_TEMPLATE/feature_request.md and inspect the YAML front matter, especially the labels: key between title: and assignees:. Confirm that only the feature request label changes, then after the PR merges to main, use the issue template chooser to verify the draft shows enhancement rather than documentation and close the draft without submitting.

Written by the indexing model from the issue text.