chore: edit PR template

Author: yyx990803

.github/pull_request_template.md

@@ -12,13 +12,16 @@
   https://github.com/<USERNAME>/rfcs/blob/<BRANCH>/active-rfcs/0000-my-proposal.md
   You can find this link by navigating to this file on your branch.
 -->
+
 - [Full Rendered Proposal]()
 
 <!--
-  Please open and link to a corresponding discussion thread (under "Discussion" tab of the repo). Make sure to:
-  - Reference PR #id in its title.
-  - Link to this RFC in its body.
+  Please open and link to a corresponding discussion thread
+  (under "Discussion" tab of the repo).
+  After submitting the PR, make sure to edit the discussion
+  to link to this PR.
 -->
+
 - [Discussion Thread]()
 
 <!-- include additional links to related issues if applicable -->