"Expand" and "Collapse" context menu items display submenu arrows in the Graph Toolkit transition Inspector even though they have no submenus

How to reproduce:
1. Import the attached script "MySM"
2. In the Project window, Create -> My State Machine and open the Asset
3. In the workspace, right-click -> Create State -> add any two states
4. Drag a transition from the first State to the second State
5. Select the transition and open the Inspector
6. Right-click the transition rule row in the Inspector
7. Observe the results

Expected results: The "Expand" and "Collapse" menu items do not display a submenu indicator arrow
Actual results: The "Expand" and "Collapse" menu items display "▶" and "◀" arrows in the position reserved for submenu indicators, and hovering them opens no submenu

Reproducible with: 6000.7.0a5

Reproducible on: macOS Tahoe 26 (M1)
Not reproducible on: No other environment tested

Note: The arrows are the Right Arrow and Left Arrow keyboard shortcut hints produced by the "Expand _RIGHT" and "Collapse _LEFT" menu strings in TransitionPropertiesEditor. Unity renders named arrow keys as glyphs in the same right-aligned slot used for the submenu indicator, so the shortcut hint looks similar to the expandable menu.