build: Exclude demo folder too from sdist #11

Job	Run time
pre-commit / pre-commit	58s
pre-commit / lint-extension	2m 14s
codeql / codeql	3m 59s
test-pip / test-pip (3.8, ~=2.0, true)	14m 1s
test-conda / test-conda (ubuntu-latest, 3.9)	16m 46s
test-pip / test-pip (3.9, ~=2.0, true)	10m 38s
test-conda / test-conda (macos-latest, 3.9)	26m 25s
test-pip / test-pip (3.10, ~=2.0, true)	10m 38s
test-conda / test-conda (windows-latest, 3.9)	16m 44s
test-pip / test-pip (3.11, ~=2.0, true)	10m 21s
test-pip / test-pip (3.12-dev, true)	10m 48s
test-pip / test-pip (3.13-dev, true)	4m 0s
test-pip / test-pip (3.x)	8m 49s
test-pip / test-pip (3.x, ~=3.0)	11m 3s
test-pip / test-pip (3.11, ~=4.0, true)	2m 18s
test-pip / test-pip (3.x, false)	10m 32s
test-pip / test-pip (3.x, true, true)	13m 35s
build / build	3m 11s
pass	3s
	2h 57m 3s

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