docs: Fix format of issue template checkbox (#846)

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## Description

Fix the format of the label for the checkbox asking whether you want to
work in the issue.

## Type of Change

<!--- Put an `x` in all the boxes that apply: -->

- [ ] ✨ `feat` -- New feature (non-breaking change which adds
functionality)
- [ ] 🛠️ `fix` -- Bug fix (non-breaking change which fixes an issue)
- [ ] ❌ `!` -- Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] 🧹 `refactor` -- Code refactor
- [ ] ✅ `ci` -- Build configuration change
- [x] 📝 `docs` -- Documentation
- [ ] 🗑️ `chore` -- Chore

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -87,5 +87,5 @@ body:
     attributes:
       label: Other
       options:
-        - label: I'm interested in working on a PR for this:
+        - label: I'm interested in working on a PR for this.
 

.github/ISSUE_TEMPLATE/feature_request.yml

@@ -63,5 +63,5 @@ body:
     attributes:
       label: Other
       options:
-        - label: I'm interested in working on a PR for this:
+        - label: I'm interested in working on a PR for this.