Update PR template: Simplify

Simplify PR template as it isn't shown with markdown formatting when creating a PR

PULL_REQUEST_TEMPLATE.md

@@ -1,10 +1,3 @@
-**Pull Requests should use the `master` branch by default.**
+Pull Requests should use the master branch by default.
 
-**Only make Pull Requests against other branches (e.g. `2.1` or `3.0`) if your changes only apply to that specific version of Godot.**
-
-Things to keep in mind:
-
-- [Godot docs writing guidelines](http://docs.godotengine.org/en/latest/community/contributing/docs_writing_guidelines.html)
-- [Godot pull request workflow](http://docs.godotengine.org/en/latest/community/contributing/pr_workflow.html)
-- If you need help with your PR, [#documentation on Discord](https://godotengine.org/community) is probably a good first starting point
-- For large changes, it may make sense to discuss them in advance and maybe create an issue to let others know you're working on this
+Only make Pull Requests against other branches (e.g. 2.1 or 3.0) if your changes only apply to that specific version of Godot.