Amend changelog typo + prepare for next 4.x releases

Author: stronk7

.github/workflows/release.yml

@@ -42,4 +42,4 @@ jobs:
             ${{ steps.extract-release-notes.outputs.release_notes }}
             #
             Take a look at the [CHANGELOG](https://moodlehq.github.io/moodle-plugin-ci/CHANGELOG.html) for details about other releases.
-            Please follow [3.0 Upgrade guide](https://moodlehq.github.io/moodle-plugin-ci/UPGRADE-3.0.html) when upgrading from 2.x.
+            Please follow the [4.0 Upgrade guide](https://moodlehq.github.io/moodle-plugin-ci/UPGRADE-4.0.html) when upgrading from 3.x.

docs/CHANGELOG.md

@@ -25,7 +25,7 @@ The format of this change log follows the advice given at [Keep a CHANGELOG](htt
 
 ### Removed
 - Support for PHP < 7.4 (the new minimum version).
-- Support for Moodle < 3.8.3, that was the [first release officially supporting PHP 7.4](https://moodledev.io/general/development/policies/php#php-74)).
+- Support for Moodle < 3.8.3, that was the [first release officially supporting PHP 7.4](https://moodledev.io/general/development/policies/php#php-74).
 
 ## [3.4.12] - 2023-05-03
 ### Changed