Reorder the checkboxes in the PR template (flutter#3666)

...so that they are listed in more or less the likely order that people will do them in.

Author: Hixie

.github/PULL_REQUEST_TEMPLATE.md

@@ -6,16 +6,16 @@
 
 ## Pre-launch Checklist
 
-- [ ] The title of the PR starts with the name of the plugin surrounded by square brackets, e.g. `[shared_preferences]`
 - [ ] I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
 - [ ] I read the [Tree Hygiene] wiki page, which explains my responsibilities.
 - [ ] I read and followed the [Flutter Style Guide] and the [C++, Objective-C, Java style guides].
+- [ ] I signed the [CLA].
+- [ ] The title of the PR starts with the name of the plugin surrounded by square brackets, e.g. `[shared_preferences]`
 - [ ] I listed at least one issue that this PR fixes in the description above.
-- [ ] I added new tests to check the change I am making or feature I am adding, or Hixie said the PR is test exempt.
 - [ ] I updated pubspec.yaml with an appropriate new version according to the [pub versioning philosophy].
 - [ ] I updated CHANGELOG.md to add a description of the change.
 - [ ] I updated/added relevant documentation (doc comments with `///`).
-- [ ] I signed the [CLA].
+- [ ] I added new tests to check the change I am making or feature I am adding, or Hixie said the PR is test exempt.
 - [ ] All existing and new tests are passing.
 
 If you need help, consider asking for advice on the #hackers-new channel on [Discord].