Update CONTRIBUTING.md (umbraco#7680)

* Update CONTRIBUTING.md

Syncs header name with summary and fixes link syntax

* Update CONTRIBUTING.md

Changed header back and updated summary instead

.github/CONTRIBUTING.md

@@ -28,7 +28,7 @@ This project and everyone participating in it, is governed by the [our Code of C
 [Working with the code](#working-with-the-code)
   * [Building Umbraco from source code](#building-umbraco-from-source-code)
   * [Working with the source code](#working-with-the-source-code)
-  * [Making changes after the PR was opened](#making-changes-after-the-pr-was-opened)
+  * [Making changes after the PR is open](#making-changes-after-the-pr-is-open)
   * [Which branch should I target for my contributions?](#which-branch-should-i-target-for-my-contributions)
   * [Keeping your Umbraco fork in sync with the main repository](#keeping-your-umbraco-fork-in-sync-with-the-main-repository)
 
@@ -65,7 +65,7 @@ Great question! The short version goes like this:
   * **Change** - make your changes, experiment, have fun, explore and learn, and don't be afraid. We welcome all contributions and will [happily give feedback](#questions)
   * **Commit** - done? Yay! 🎉 **Important:** create a new branch now and name it after the issue you're fixing, we usually follow the format: `temp-12345`. This means it's a temporary branch for the particular issue you're working on, in this case `12345`. When you have a branch, commit your changes. Don't commit to `v8/contrib`, create a new branch first.
   * **Push** - great, now you can push the changes up to your fork on GitHub
-  * **Create pull request** - exciting! You're ready to show us your changes (or not quite ready, you just need some feedback to progress - you can now make use of GitHub's draft pull request status, detailed [here] (https://github.blog/2019-02-14-introducing-draft-pull-requests/)). GitHub has picked up on the new branch you've pushed and will offer to create a Pull Request. Click that green button and away you go.
+  * **Create pull request** - exciting! You're ready to show us your changes (or not quite ready, you just need some feedback to progress - you can now make use of GitHub's draft pull request status, detailed [here](https://github.blog/2019-02-14-introducing-draft-pull-requests/)). GitHub has picked up on the new branch you've pushed and will offer to create a Pull Request. Click that green button and away you go.
 
   ![Create a pull request](img/createpullrequest.png)