Update phpunit framework to most recent version

Signed-off-by: Christian Wolf <github@christianwolf.email>

.github/actions/run-tests/tests/install.sh

@@ -18,7 +18,7 @@ function configure_gd_without ()
 
 function configure_gd()
 {
-	if [ "$1" = "7.2" ]; then
+	if [ "$1" = "7.2" -o "$1" = "7.3" ]; then
 		configure_gd_without
 		return $?
 	else

composer.json

@@ -12,6 +12,7 @@
       "ext-libxml": "*"
     },
     "require-dev": {
-        "phpunit/phpunit": "^5.4"
+        "phpunit/phpunit": ">=9.0",
+        "nikic/php-parser": "4.2"
     }
 }