remove PHPUnit 9 constraint

Author: llaville

CHANGELOG.md

@@ -11,6 +11,10 @@ using the [Keep a CHANGELOG](http://keepachangelog.com) principles.
 
 - [Mega-Linter](https://github.com/nvuillam/mega-linter) support as QA tool to avoid technical debt
 
+### Changed
+
+- As PHPUnit 9 is not supported due to issue PHPUnit #4754, we removed composer constraint accordingly
+
 ## [2.1.0] - 2021-08-12
 
 **CAUTION** : PHPUnit 9 is not supported due to issue PHPUnit [#4754](https://github.com/sebastianbergmann/phpunit/issues/4754)

composer.json

@@ -11,7 +11,7 @@
     "require": {
         "php": "^7.2|^8.0",
         "psr/log": "^1.0|^2.0|^3.0",
-        "phpunit/phpunit": "^7.5|^8.0|^9.0"
+        "phpunit/phpunit": "^7.5|^8.0"
     },
     "require-dev": {
         "monolog/monolog": "^2.0",