docs: documented very_good test argument terminator #396

Job	Run time
e2e (3.13.0, test/commands/test/async_main/async_main_test.dart)	1m 46s
e2e (3.13.0, test/commands/test/compilation_error/compilation_error_test.dart)	1m 57s
e2e (3.13.0, test/commands/test/no_project/no_project_test.dart)	1m 16s
e2e (3.13.0, test/commands/test/spaced_golden_file_name/spaced_golden_file_name_test.dart)	1m 52s
e2e (3.13.0, test/commands/create/flutter_app/core_test.dart)	3m 39s
e2e (3.13.0, test/commands/create/dart_cli/dart_cli_test.dart)	2m 34s
e2e (3.13.0, test/commands/create/dart_package/dart_pkg_test.dart)	1m 47s
e2e (3.13.0, test/commands/create/docs_site/docs_site_test.dart)	3m 16s
e2e (3.13.0, test/commands/create/flutter_package/flutter_pkg_test.dart)	1m 57s
e2e (3.13.0, test/commands/create/flutter_plugin/flutter_plugin_test.dart)	5m 18s
e2e (any, test/commands/test/async_main/async_main_test.dart)	1m 45s
e2e (any, test/commands/test/compilation_error/compilation_error_test.dart)	3m 40s
e2e (any, test/commands/test/no_project/no_project_test.dart)	1m 35s
e2e (any, test/commands/test/spaced_golden_file_name/spaced_golden_file_name_test.dart)	2m 7s
e2e (any, test/commands/create/flutter_app/core_test.dart)	2m 32s
e2e (any, test/commands/create/dart_cli/dart_cli_test.dart)	1m 58s
e2e (any, test/commands/create/dart_package/dart_pkg_test.dart)	2m 8s
e2e (any, test/commands/create/docs_site/docs_site_test.dart)	2m 29s
e2e (any, test/commands/create/flutter_package/flutter_pkg_test.dart)	2m 33s
e2e (any, test/commands/create/flutter_plugin/flutter_plugin_test.dart)	6m 24s
	52m 33s

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