Fix `test_window_state_assignment` testbed on macOS-arm64 #7355

Job	Run time
Pre-commit checks / Pre-commit Checks	42s
Check towncrier / Towncrier Checks	35s
Package Toga (android) / Create Python Package	27s
Package Toga (cocoa) / Create Python Package	17s
Package Toga (core) / Create Python Package	15s
Package Toga (demo) / Create Python Package	18s
Package Toga (dummy) / Create Python Package	17s
Package Toga (gtk) / Create Python Package	17s
Package Toga (iOS) / Create Python Package	24s
Package Toga (textual) / Create Python Package	18s
Package Toga (toga) / Create Python Package	23s
Package Toga (web) / Create Python Package	24s
Package Toga (winforms) / Create Python Package	25s
Test core (macos-latest, 3.9)	1m 32s
Test core (macos-latest, 3.10)	1m 8s
Test core (macos-latest, 3.11)	1m 4s
Test core (macos-latest, 3.12)	1m 6s
Test core (macos-latest, 3.13)	50s
Test core (ubuntu-latest, 3.9)	48s
Test core (ubuntu-latest, 3.10)	52s
Test core (ubuntu-latest, 3.11)	1m 4s
Test core (ubuntu-latest, 3.12)	1m 10s
Test core (ubuntu-latest, 3.13)	1m 5s
Test core (windows-latest, 3.9)	1m 37s
Test core (windows-latest, 3.10)	1m 33s
Test core (windows-latest, 3.11)	1m 42s
Test core (windows-latest, 3.12)	1m 37s
Test core (windows-latest, 3.13)	2m 17s
Coverage	27s
Testbed (macOS-x86_64)	8m 29s
Testbed (macOS-arm64)	6m 38s
Testbed (windows)	8m 0s
Testbed (linux-x11)	5m 16s
Testbed (linux-wayland)	5m 10s
Testbed (android)	10m 25s
Testbed (iOS)	6m 47s
Testbed (textual-linux)	54s
Testbed (textual-macOS)	1m 22s
Testbed (textual-windows)	2m 2s
	1h 19m 57s

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