Fix lowercase letter KeySym regressions #1303

Job	Run time
ruff	9s
mypy	21s
sdist	1m 16s
parse_sdl (macos-latest, 3.2.16)	22s
parse_sdl (windows-latest, 3.2.16)	1m 34s
test-docs	4m 45s
build (windows-latest, 3.10, x64)	2m 56s
build (ubuntu-latest, 3.10, x64)	5m 30s
build (windows-latest, pypy-3.10, x64)	4m 21s
build (windows-latest, 3.10, x86)	4m 18s
build-macos (pp310-*)	5m 24s
linux-wheels (x86_64, pp310-manylinux*)	3m 43s
pyodide	3m 13s
linux-wheels (x86_64, cp310-manylinux*)	4m 7s
build-macos (cp310-*_universal2)	2m 29s
build (ubuntu-latest, pypy-3.10, x64)	4m 44s
linux-wheels (aarch64, cp310-manylinux*)	4m 2s
tox (ubuntu-latest)	2m 27s
linux-wheels (aarch64, pp310-manylinux*)	3m 26s
publish	0s
	59m 7s

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