build: upgrade to PHPUnit 11

Signed-off-by: Sacha Telgenhof <me@sachatelgenhof.com>

Author: stelgenhof

.gitignore

@@ -3,6 +3,7 @@
 .php-cs-fixer.cache
 .php_cs.cache
 .phpactor.json
+.phpunit.cache
 .phpunit.result.cache
 bin/_*
 composer.lock

composer.json

@@ -45,7 +45,7 @@
     "mikey179/vfsstream": "^1.6",
     "phpstan/phpstan": "^2.1",
     "phpstan/phpstan-deprecation-rules": "^2.0",
-    "phpunit/phpunit": "^8.5 || ^9.6"
+    "phpunit/phpunit": "^11.5"
   },
   "suggest": {
     "ext-calendar": "For calculating the date of Easter"