Steps to reproduce:
1. Create/Open any Unity project
2. Open Window -> Rendering -> Lighting Window
3. Open Window -> Analysis -> IMGUI Debugger
4. Select Lighting Window as Inspected View in IMGUI Debugger
5. Check the assigned font of "Toolbar (LargeButtonLeft)", "Toolbar (LargeButtonMid)", "Toolbar (LargeButtonRight)"

Expected result: All of the buttons use the same font and there is no visual difference between mid and outer button text
Actual result: Inner and outer toolbar button text font looks slightly different, "Toolbar (LargeButtonMid)" has an assigned font while "Toolbar (LargeButtonLeft)" and "Toolbar (LargeButtonRight)" do not have an assigned font

Reproduced with: 2019.4.23f1, 2021.2.0a12

Note: this affects all GUILayout.Toolbar instances in the editor where the toolbar has 3 or more buttons (Lighting Window, Light Explorer Window, Navigation Window, Occlusion Culling)