chore: migrate GH issue template to issue form

See https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/configuring-issue-templates-for-your-repository#creating-issue-forms

.github/ISSUE_TEMPLATE/bug-report.yml

@@ -76,7 +76,6 @@ body:
     attributes:
       label: What Hugo Module versions does your site use?
       description: Paste your `go.mod` here.
-      placeholder: ''
     validations:
       required: true
   - type: dropdown