java/lang/StringBuffer/HugeCapacity.java and j/l/StringBuilder/HugeCapacity.java tests shouldn't be @ignore-d

both java/lang/StringBuffer/HugeCapacity.java and java/lang/StringBuilder/HugeCapacity.java tests have '@ignore This test has huge memory requirements' and '@requires os.maxMemory >= 6G', having @requires is enough to guarantee that the tests won't be executed on the testing environment which can't handle such requirement, in other words, @ignore just removed the tests from execution for no good reasons.