Update Garbage Collector Test case
After #3 (closed) is done, modify the 2nd test case of Garbage collector. ( search for TODO in https://dbgit.prakinf.tu-ilmenau.de/code/poseidon_core/blob/master/test/transaction_test.cpp)
After #3 (closed) is done, modify the 2nd test case of Garbage collector. ( search for TODO in https://dbgit.prakinf.tu-ilmenau.de/code/poseidon_core/blob/master/test/transaction_test.cpp)