chore: fix typo in PULL_REQUEST_TEMPLATE (#5750)

.github/PULL_REQUEST_TEMPLATE

@@ -34,7 +34,7 @@
 - [ ] Update the documentation to include this new feature.
 - [ ] Tests(including UT, IT, E2E) are added to verify the new feature.
 - [ ] If it's UI related, attach the screenshots below.
-     ==== 🆕 Remove this line WHEN AND ONLY WHEN you're improving the performance, follow the checklist 👆 ==== -->
+     ==== 🆕 Remove this line WHEN AND ONLY WHEN you're adding a new feature, follow the checklist 👆 ==== -->
 
 - [ ] If this pull request closes/resolves/fixes an existing issue, replace the issue number. Closes #<issue number>.
 - [ ] Update the [`CHANGES` log](https://github.com/apache/skywalking/blob/c2141978d1039375598a32418b75161a78da22c1/CHANGES.md).