chore: Remove half-implemented changelog automation (#1564)

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

CONTRIBUTING.md

@@ -20,55 +20,3 @@ Prometheus uses GitHub to manage reviews of pull requests.
   Environments](http://peter.bourgon.org/go-in-production/#formatting-and-style).
 
 * Be sure to sign off on the [DCO](https://github.com/probot/dco#how-it-works)
-
-## How to write a PR description
-
-### Describe your PR
-
-In this section, provide a clear and concise description of what your PR does. This helps reviewers understand the purpose and context of your changes.
-
-### What type of PR is this?
-
-Indicate the type of PR by adding one of the following options:
-
-- `/kind fix`
-- `/kind bugfix`
-- `/kind enhancement`
-- `/kind feature`
-- `/kind feat`
-- `/kind change`
-- `/kind release-note-none`
-
-If this change should not appear in the changelog, use `/kind release-note-none`.
-
-Example 1:
-```
-  ### What type of PR is this?
-  /kind feature
-```
-
-Example 2:
-```
-  ### What type of PR is this?
-  /kind release-note-none
-```
-
-### Changelog Entry
-
-Include a brief summary of your change for the changelog. This helps users understand what has been modified, added, or fixed in the project. If your change should not appear in the changelog, write `NONE`. Make sure to add only user-facing changes.
-
-Example 1:
-```
-	### Changelog Entry
-	```release-note
-	api: Switch to POST for `LabelNames`.
-	```
-```
-
-Example 2:
-```
-	### Changelog Entry
-	```release-note
-	NONE
-	```
-```