remove invalid attribute from phpunit.xml

Author: sgiehl

phpunit.xml

@@ -7,7 +7,6 @@
          convertWarningsToExceptions="true"
          processIsolation="false"
          stopOnFailure="false"
-         syntaxCheck="false"
          bootstrap="./vendor/autoload.php">
 
     <testsuites>
@@ -16,4 +15,4 @@
         </testsuite>
     </testsuites>
 
-</phpunit>
+</phpunit>