Migrate phpunit configuration

Done with `phpunit --migrate-configuration`.

phpunit.xml

@@ -1,24 +1,13 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         backupGlobals="false"
-         backupStaticAttributes="false"
-         bootstrap="vendor/autoload.php"
-         colors="true"
-         convertErrorsToExceptions="true"
-         convertNoticesToExceptions="true"
-         convertWarningsToExceptions="true"
-         processIsolation="false"
-         stopOnFailure="false"
-         printerClass="Sempro\PHPUnitPrettyPrinter\PrettyPrinterForPhpUnit9"
-         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd">
-  <coverage processUncoveredFiles="true">
-    <include>
-      <directory suffix=".php">./src</directory>
-    </include>
-  </coverage>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" backupGlobals="false" bootstrap="vendor/autoload.php" colors="true" processIsolation="false" stopOnFailure="false" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/11.0/phpunit.xsd" cacheDirectory=".phpunit.cache" backupStaticProperties="false">
   <testsuites>
     <testsuite name="Suite">
       <directory suffix="Test.php">./tests</directory>
     </testsuite>
   </testsuites>
+  <source>
+    <include>
+      <directory suffix=".php">./src</directory>
+    </include>
+  </source>
 </phpunit>