Remove the unused pull_request_template.md file

[Nicolapps]

Summary

Fixes #381

Removes the .github/pull_request_template.md file, which serves the same purposes as .github/PULL_REQUEST_TEMPLATE.md but is less recent.

---

For us to review and ship your PR efficiently, please perform the following steps:

• [x] Open a bug/issue before writing your code 🧑‍💻. This ensures we can discuss the changes and get feedback from everyone that should be involved. If you`re fixing a typo or something that`s on fire 🔥 (e.g. incident related), you can skip this step.
• [x] Read the contribution guidelines 📖. This ensures your code follows our style guide and passes our tests.
• [x] Update or add tests (if any source code was changed or added) 🧪
• [x] Update or add documentation (if features were changed or added) 📝
• [x] Make sure the status checks below are successful ✅

A picture of a cute animal (not mandatory, but encouraged)