Fix deprecation warning in leak test

Author: msimacek

graalpython/com.oracle.graal.python.test/src/com/oracle/graal/python/test/advanced/LeakTest.java

@@ -346,11 +346,6 @@ protected String getLanguageId() {
         return languageId;
     }
 
-    @Override
-    protected String[] getDefaultLanguages() {
-        return new String[]{languageId};
-    }
-
     @Override
     protected void printHelp(OptionCategory maxCategory) {
         System.out.println("--lang ID --code CODE --forbidden-class FQN [--forbidden-class FQN]* [--shared-engine] [--keep-dump] [POLYGLOT-OPTIONS]");