Simplify PR template. (#1080)

Simplifies PR template to match recent updates for cuDF, cuSpatial. See rapidsai/cudf#10774, rapidsai/cuspatial#617.

Authors:
  - Bradley Dice (https://github.com/bdice)

Approvers:
  - Mark Harris (https://github.com/harrism)
  - Jake Hemstad (https://github.com/jrhemstad)
  - AJ Schmidt (https://github.com/ajschmidt8)

URL: #1080

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,49 +1,9 @@
-<!--
-
-Thanks for wanting to contribute to RMM :) Please read these instructions and 
-replace them with your description.
-
-First, if you need some help or want to chat to the core developers, please
-visit https://rapids.ai/community.html for links to our Google Group and other
-communication channels.
-
-Here's some guidelines to help the review process go smoothly.
-
-0. Please write a description in this text box of the changes that are being
-   made.
-
-1. Please ensure that you have written units tests for the changes made and/or
-   features added.
-
-2. If you are closing an issue please use one of the automatic closing words as
-   noted here: https://help.github.com/articles/closing-issues-using-keywords/
-
-3. If your pull request is not ready for review but you want to make use of the
-   continuous integration testing facilities please label it with `[WIP]`.
-
-4. If your pull request is ready to be reviewed without requiring additional
-   work on top of it, then remove the `[WIP]` label (if present) and replace
-   it with `[REVIEW]`. If assistance is required to complete the functionality,
-   for example when the C/C++ code of a feature is complete but Python bindings
-   are still required, then add the label `[HELP-REQ]` so that others can triage
-   and assist. The additional changes then can be implemented on top of the
-   same PR. If the assistance is done by members of the rapidsAI team, then no
-   additional actions are required by the creator of the original PR for this,
-   otherwise the original author of the PR needs to give permission to the
-   person(s) assisting to commit to their personal fork of the project. If that
-   doesn't happen then a new PR based on the code of the original PR can be
-   opened by the person assisting, which then will be the PR that will be
-   merged.
-
-5. Once all work has been done and review has taken place please do not add
-   features or make changes out of the scope of those requested by the reviewer
-   (doing this just adds delays as already reviewed code ends up having to be
-   re-reviewed/it is hard to tell what is new etc!). Further, please do not
-   rebase your branch on master/force push/rewrite history, doing any of these
-   causes the context of any comments made by reviewers to be lost. If
-   conflicts occur against the release or master branch they should be resolved 
-   by merging master into the branch used for making the pull request.
-
-Many thanks in advance for your cooperation!
-
--->
+## Description
+<!-- Provide a standalone description of changes in this PR. -->
+<!-- Reference any issues closed by this PR with "closes #1234". -->
+<!-- Note: The pull request title will be included in the CHANGELOG. -->
+
+## Checklist
+- [ ] I am familiar with the [Contributing Guidelines](https://github.com/rapidsai/rmm/blob/HEAD/CONTRIBUTING.md).
+- [ ] New or existing tests cover these changes.
+- [ ] The documentation is up to date with these changes.