Remove preview section from PR template (#638)

Removed the preview section from the pull request template.

Author: zliang-akamai

.github/pull_request_template.md

@@ -7,7 +7,3 @@
 **What are the steps to reproduce the issue or verify the changes?**
 
 **How do I run the relevant unit/integration tests?**
-
-## 📷 Preview
-
-**If applicable, include a screenshot or code snippet of this change. Otherwise, please remove this section.**