fix: pull request template typo
<!--- Why is this change required? What problem does it solve? -->
-## Screenshots (if appropriate):
+## Screenshots (if appropriate)
## Types of changes
- [ ] Breaking change (fix or feature that would cause existing functionality to change)
- [ ] Documentation Update (if none of the other choices apply)
-## Checklist:
+## Checklist
<!--- Go over all the following points, and put an `x` in all the boxes that apply. -->
<!--- If you're unsure about any of these, don't hesitate to ask. We're here to help! -->
