On X11, simplify available_monitors() impl #89

Job	Run time
Check formatting	7s
Run cargo-deny on Android	19s
Run cargo-deny on iOS	20s
Run cargo-deny on Linux	21s
Test stable Windows 64bit MSVC	1m 55s
Run cargo-deny on macOS	20s
Test stable Windows 32bit MSVC	1m 45s
Run cargo-deny on Redox OS	22s
Run cargo-deny on web	20s
Run cargo-deny on Windows	20s
Test stable Windows 64bit GNU	2m 17s
Test stable Windows 32bit GNU	2m 20s
Test stable Linux 32bit	2m 45s
Test stable Linux 64bit	2m 36s
Test stable X11	2m 14s
Test stable Wayland	2m 29s
Test stable Android	1m 3s
Test stable Redox OS	25s
Test stable macOS	2m 22s
Test stable iOS x86_64	1m 46s
Test stable iOS Aarch64	2m 40s
Test stable web	1m 7s
Test nightly Windows 64bit MSVC	1m 42s
Test nightly Windows 32bit MSVC	1m 42s
Test nightly Windows 64bit GNU	2m 4s
Test nightly Windows 32bit GNU	2m 4s
Test nightly Linux 32bit	2m 35s
Test nightly Linux 64bit	2m 28s
Test nightly X11	2m 18s
Test nightly Wayland	2m 18s
Test nightly Android	59s
Test nightly Redox OS	22s
Test nightly macOS	2m 0s
Test nightly iOS x86_64	1m 50s
Test nightly iOS Aarch64	1m 17s
Test nightly web	1m 0s
Test 1.70.0 Windows 64bit MSVC	50s
Test 1.70.0 Windows 32bit MSVC	58s
Test 1.70.0 Windows 64bit GNU	1m 3s
Test 1.70.0 Windows 32bit GNU	1m 5s
Test 1.70.0 Linux 32bit	1m 21s
Test 1.70.0 Linux 64bit	58s
Test 1.70.0 X11	45s
Test 1.70.0 Wayland	46s
Test 1.70.0 Redox OS	27s
Test 1.70.0 macOS	1m 47s
Test 1.70.0 iOS x86_64	57s
Test 1.70.0 iOS Aarch64	55s
Test 1.70.0 web	39s
Test 1.70.0 Android	35s
	1h 7m 58s

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