unpaper: fix regex #575

Job	Run time
Build sdist and wheels	14s
Test macOS (macos-latest, 3.10)	4m 34s
Test Windows (windows-latest, 3.10)	7m 26s
Test ubuntu-22.04 with Python 3.10	5m 6s
Test macOS (macos-latest, 3.11)	4m 30s
Test Windows (windows-latest, 3.11)	7m 25s
Test macOS (macos-latest, 3.12)	4m 41s
Test Windows (windows-latest, 3.12)	8m 4s
Test ubuntu-22.04 with Python 3.11	4m 57s
Test macOS (macos-latest, 3.13)	4m 27s
Test Windows (windows-latest, 3.13)	7m 47s
Test ubuntu-22.04 with Python 3.12	5m 26s
Test macOS (macos-13, 3.10)	9m 8s
Test ubuntu-22.04 with Python 3.13	5m 10s
Test macOS (macos-13, 3.11)	7m 38s
Test ubuntu-24.04 with Python 3.10	4m 31s
Test macOS (macos-13, 3.12)	7m 15s
Test ubuntu-24.04 with Python 3.11	4m 32s
Test macOS (macos-13, 3.13)	10m 31s
Test ubuntu-24.04 with Python 3.12	5m 0s
Test ubuntu-24.04 with Python 3.13	4m 45s
Test ubuntu-24.04 with Python pypy3.10	10m 19s
Build Alpine-based Docker images	3m 20s
Build Ubuntu-based Docker image	9m 0s
Deploy artifacts to PyPI	0s
Create GitHub release	0s
	2h 25m 46s

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