Issue #2209337 by tstoeckler: Remove hidden property from test extensions.

...s/action/tests/action_bulk_test/action_bulk_test.info.yml

...or/tests/modules/aggregator_test/aggregator_test.info.yml

...ules/aggregator_test_views/aggregator_test_views.info.yml

...ests/modules/custom_block_test/custom_block_test.info.yml

...odules/block/tests/modules/block_test/block_test.info.yml

...specialchars_theme/block_test_specialchars_theme.info.yml

...ck_test/themes/block_test_theme/block_test_theme.info.yml

.../tests/modules/block_test_views/block_test_views.info.yml

...emes/breakpoint_test_theme/breakpoint_test_theme.info.yml

core/modules/ckeditor/tests/modules/ckeditor_test.info.yml

...odules/color/tests/modules/color_test/color_test.info.yml

...or_test/themes/color_test_theme/color_test_theme.info.yml

.../comment/tests/modules/comment_test/comment_test.info.yml

...ts/modules/comment_test_views/comment_test_views.info.yml

...nfig/tests/config_events_test/config_events_test.info.yml

...nfig/tests/config_import_test/config_import_test.info.yml

.../config_integration_test/config_integration_test.info.yml

...g_other_module_config/config_other_module_config.info.yml

...les/config/tests/config_override/config_override.info.yml

...onfig/tests/config_override_test/config_override_test.yml