Update testnet time of hf28 and set time of hf27 to const value
By mistake, time of HF27 was not set to const value and time of HF28 in testnet was too far, which make testing impossible.
Additionally trimmed trailing spaces in modified files
in relation to: !843 (merged)
failed pipeline: https://gitlab.syncad.com/hive/hive/-/pipelines/61299/test_report test name: functional.python_tests.api_tests.account_history_api_tests.test_enum_virtual_ops