Fix `test_window_state_assignment` testbed on macOS-arm64 #7356

Job	Run time
Check towncrier / Towncrier Checks	29s
Pre-commit checks / Pre-commit Checks	37s
Package Toga (cocoa) / Create Python Package	15s
Package Toga (android) / Create Python Package	25s
Package Toga (core) / Create Python Package	25s
Package Toga (demo) / Create Python Package	21s
Package Toga (dummy) / Create Python Package	25s
Package Toga (gtk) / Create Python Package	22s
Package Toga (iOS) / Create Python Package	18s
Package Toga (textual) / Create Python Package	31s
Package Toga (toga) / Create Python Package	26s
Package Toga (web) / Create Python Package	23s
Package Toga (winforms) / Create Python Package	25s
Test core (macos-latest, 3.9)	1m 14s
Test core (macos-latest, 3.10)	1m 19s
Test core (macos-latest, 3.11)	44s
Test core (macos-latest, 3.12)	1m 11s
Test core (macos-latest, 3.13)	57s
Test core (ubuntu-latest, 3.9)	59s
Test core (ubuntu-latest, 3.10)	53s
Test core (ubuntu-latest, 3.11)	52s
Test core (ubuntu-latest, 3.12)	1m 3s
Test core (ubuntu-latest, 3.13)	1m 6s
Test core (windows-latest, 3.9)	1m 47s
Test core (windows-latest, 3.10)	1m 51s
Test core (windows-latest, 3.11)	1m 33s
Test core (windows-latest, 3.12)	1m 40s
Test core (windows-latest, 3.13)	2m 12s
Testbed (macOS-x86_64)	8m 17s
Testbed (macOS-arm64)	6m 36s
Testbed (windows)	7m 0s
Coverage	29s
Testbed (linux-x11)	5m 5s
Testbed (linux-wayland)	5m 12s
Testbed (android)	13m 0s
Testbed (iOS)	8m 3s
Testbed (textual-linux)	55s
Testbed (textual-macOS)	59s
Testbed (textual-windows)	1m 59s
	1h 22m 18s

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