[23.2] Fix CSS issue affecting all dropdown menus

[davelopez]

Follow up to #17112

This fixes a CSS side-effect issue affecting all dropdown menus caught by the selenium tests.

Should fix all the selenium tests that are failing with:

FAILED lib/galaxy_test/selenium/test_pages_index.py::TestPagesIndex::test_page_deletion - AssertionError: Failed to find page action option with title [Delete]
FAILED lib/galaxy_test/selenium/test_workflow_editor.py::TestWorkflowEditor::test_edit_license - AssertionError: Failed to find workflow action option with title [Edit]
FAILED lib/galaxy_test/selenium/test_workflow_editor.py::TestWorkflowEditor::test_optional_select_data_field - AssertionError: Failed to find workflow action option with title [Edit]
FAILED lib/galaxy_test/selenium/test_workflow_editor.py::TestWorkflowEditor::test_non_data_connections - AssertionError: Failed to find workflow action option with title [Edit]
FAILED lib/galaxy_test/selenium/test_workflow_editor.py::TestWorkflowEditor::test_reconnecting_nodes - AssertionError: Failed to find workflow action option with title [Edit]
FAILED lib/galaxy_test/selenium/test_workflow_editor.py::TestWorkflowEditor::test_simple_mapping_connections - AssertionError: Failed to find workflow action option with title [Edit]
FAILED lib/galaxy_test/selenium/test_workflow_editor.py::TestWorkflowEditor::test_change_datatype - AssertionError: Failed to find workflow action option with title [Edit]
FAILED lib/galaxy_test/selenium/test_workflow_editor.py::TestWorkflowEditor::test_conditional_subworkflow_step - AssertionError: Failed to find workflow action option with title [Edit]
FAILED lib/galaxy_test/selenium/test_workflow_editor.py::TestWorkflowEditor::test_editor_invalid_tool_state - AssertionError: Failed to find workflow action option with title [Edit]
FAILED lib/galaxy_test/selenium/test_workflow_editor.py::TestWorkflowEditor::test_insert_input_handling - AssertionError: Failed to find workflow action option with title [Edit]
FAILED lib/galaxy_test/selenium/test_workflow_management.py::TestWorkflowManagement::test_download - AssertionError: Failed to find workflow action option with title [Download]
FAILED lib/galaxy_test/selenium/test_workflow_sharing.py::TestWorkflowSharing::test_sharing_workflow_by_email - AssertionError: Failed to find workflow action option with title [Share]
FAILED lib/galaxy_test/selenium/test_workflow_sharing.py::TestWorkflowSharing::test_unsharing_workflow - AssertionError: Failed to find workflow action option with title [Share]
FAILED lib/galaxy_test/selenium/test_workflow_sharing.py::TestWorkflowSharing::test_sharing_with_self - AssertionError: Failed to find workflow action option with title [Share]

How to test the changes?

• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

License

• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.

[bgruening]

Thanks @davelopez