Fix the link to the CLA (#97)

Author: kylefmohr

.github/PULL_REQUEST_TEMPLATE.md

@@ -6,4 +6,4 @@
   - [ ] The pull request is done against the latest develop branch
   - [ ] Only relevant files were touched
   - [ ] Only one feature/fix was added per PR, more changes are allowed when changing boards.json
-  - [ ] I accept the [CLA](https://github.com/pioarduino/platform-espressif32/blob/develop/CONTRIBUTING.md).
+  - [ ] I accept the [CLA](https://github.com/pioarduino/platform-espressif32/blob/main/CONTRIBUTING.md#contributor-license-agreement-cla)