Update the set of propose PR branches (#627)

Author: bjgill

.github/PULL_REQUEST_TEMPLATE.md

@@ -2,7 +2,7 @@
 
 - [ ] Read the [contribution guidelines](https://github.com/openapitools/openapi-generator/blob/master/CONTRIBUTING.md).
 - [ ] Ran the shell script under `./bin/` to update Petstore sample so that CIs can verify the change. (For instance, only need to run `./bin/{LANG}-petstore.sh` and `./bin/security/{LANG}-petstore.sh` if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in `.\bin\windows\`.
-- [ ] Filed the PR against the [correct branch](https://github.com/OpenAPITools/openapi-generator/wiki/Git-Branches): `master`, `3.1.x`, `4.0.x`. Default: `master`.
+- [ ] Filed the PR against the [correct branch](https://github.com/OpenAPITools/openapi-generator/wiki/Git-Branches): `master`, `3.2.x`, `4.0.x`. Default: `master`.
 - [ ] Copied the [technical committee](https://github.com/openapitools/openapi-generator/#62---openapi-generator-technical-committee) to review the pull request if your PR is targeting a particular programming language.
 
 ### Description of the PR