test: tests guard the absence of names that were never in a release #2323

Is your feature request related to a problem? Please describe.
Under the ruling that names missing from every v* tag go unmentioned, these assertions only guard such names (each checked against git tag -l 'v*'):

• test_utilities_datetime_module_unit: test_old_module_path_is_gone, and the module and class docstrings that name pcapkit.utilities.timestamp
• test_config_unit MOVED: IPV6_TCP_WARNED_LIMIT under pcapkit.toolkit.pypcapfile (every tag that has it reads it from config; EXTENSION_HEADER_LIMIT there did ship)
• test_rfc_constants_one_home_1739_unit OLD_NAMES: IP_MAX_LENGTH (ip.py), IPV4_HEADER_LEN (ipv4.py), AH_HEADER_LEN (ah.py), TCP_MIN_HEADER_LEN and TCP_DATA_OFFSET_OCTET (tcp.py)
• L2TPVersionTests.test_ip_protocol_115_has_no_class_to_dispatch_to: the 'l2tpv3' module assertion (the TransType.L2TP dispatch check stays)
• test_conda_windows_leg_2060 test_no_step_continues_on_error: the SUMMARY ("Windows summary") and 'conda-windows' REASONS checks, which existed only between ci(conda): build and smoke-test win-64 in Conda Update, unpublished (#2060) #2067 and ci(conda): publish the win-64 package (#2060) #2138
• test_discussion_report_2030.test_a_bad_command_line_exits_2: --always and --only-if-flagged were never flags of discussion_report.py, though the docstring calls them removed

Describe the solution you'd like
Delete each listed assertion or entry and the prose naming it. Keep the rest of each test.

Additional context
Related: #1715, #1744.