Copy edit pull_request_template.md

Make minor copy edit to match our style guide to fulfill older JIRA task.

.github/pull_request_template.md

@@ -1,22 +1,23 @@
 Notes:
-* Pull requests will not be accepted until the submitter has agreed to the [contributer agreement](https://github.com/ARMmbed/mbed-os/blob/master/CONTRIBUTING.md).
-* This is just a template, so feel free to use/remove the unnecessary things
+- Pull requests will not be accepted until the submitter has agreed to the [contributer agreement](https://github.com/ARMmbed/mbed-os/blob/master/CONTRIBUTING.md).
+- This is just a template, so feel free to use/remove the unnecessary things
 
 ## Description
+
 A few sentences describing the overall goals of the pull request's commits.
 
-
 ## Status
+
 **READY/IN DEVELOPMENT/HOLD**
 
-
 ## Migrations
+
 If this PR changes any APIs or behaviors, give a short description of what *API users* should do when this PR is merged.
 
 YES | NO
 
-
 ## Related PRs
+
 List related PRs against other branches:
 
 branch | PR
@@ -24,16 +25,15 @@ branch | PR
 other_pr_production | [link]()
 other_pr_master | [link]()
 
-
 ## Todos
+
 - [ ] Tests
 - [ ] Documentation
 
-
 ## Deploy notes
-Notes regarding the deployment of this PR. These should note any
-required changes in the build environment, tools, compilers, etc.
 
+Notes regarding the deployment of this PR. These should note any required changes in the build environment, tools, compilers and so on.
 
 ## Steps to test or reproduce
+
 Outline the steps to test or reproduce the PR here.