[9.1](backport #47279) chore(github): mention stresstest script in pull request template (#47301)

* chore(github): mention stresstest script in pull request template (#47279)

* chore(github): mention stresstest script in pull request template

* Update .github/PULL_REQUEST_TEMPLATE.md

Co-authored-by: Tiago Queiroz <[email protected]>

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Co-authored-by: Tiago Queiroz <[email protected]>
(cherry picked from commit 5316421)

# Conflicts:
#	.github/PULL_REQUEST_TEMPLATE.md

* fix conflicts

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Co-authored-by: Mauri de Souza Meneguzzo <[email protected]>

Author: mergify[bot]

.github/PULL_REQUEST_TEMPLATE.md

@@ -41,7 +41,7 @@ List here all the items you have verified BEFORE sending this PR. Please DO NOT
 - [ ] I have commented my code, particularly in hard-to-understand areas
 - [ ] I have made corresponding changes to the documentation
 - [ ] I have made corresponding change to the default configuration files
-- [ ] I have added tests that prove my fix is effective or that my feature works
+- [ ] I have added tests that prove my fix is effective or that my feature works. Where relevant, I have used the [`stresstest.sh`](https://github.com/elastic/beats/blob/main/script/stresstest.sh) script to run them under stress conditions and race detector to verify their stability.
 - [ ] I have added an entry in `CHANGELOG.next.asciidoc` or `CHANGELOG-developer.next.asciidoc`.
 
 ## Disruptive User Impact