fix regex escape in _get_pandoc_urls #253

Job	Run time
test (ubuntu-20.04, 3.7)	35s
test (ubuntu-20.04, 3.8)	40s
test (ubuntu-20.04, 3.9)	40s
test (ubuntu-20.04, 3.10)	33s
test (ubuntu-20.04, 3.11)	32s
test (ubuntu-20.04, 3.12)	40s
test (ubuntu-20.04, pypy3.8)	1m 29s
test (ubuntu-20.04, pypy3.9)	52s
test (ubuntu-20.04, pypy3.10)	5m 10s
test (ubuntu-22.04, 3.7)	33s
test (ubuntu-22.04, 3.8)	44s
test (ubuntu-22.04, 3.9)	40s
test (ubuntu-22.04, 3.10)	40s
test (ubuntu-22.04, 3.11)	43s
test (ubuntu-22.04, 3.12)	1m 0s
test (ubuntu-22.04, pypy3.8)	1m 43s
test (ubuntu-22.04, pypy3.9)	47s
test (ubuntu-22.04, pypy3.10)	3m 50s
test (macos-13, 3.7)	1m 49s
test (macos-13, 3.8)	1m 44s
test (macos-13, 3.9)	1m 39s
test (macos-13, 3.10)	2m 12s
test (macos-13, 3.11)	1m 33s
test (macos-13, 3.12)	1m 55s
test (macos-13, pypy3.8)	2m 13s
test (macos-13, pypy3.9)	1m 47s
test (macos-13, pypy3.10)	8m 28s
test (windows-2022, 3.7)	3m 5s
test (windows-2022, 3.8)	2m 29s
test (windows-2022, 3.9)	2m 4s
test (windows-2022, 3.10)	2m 23s
test (windows-2022, 3.11)	2m 30s
test (windows-2022, 3.12)	2m 28s
test (windows-2022, pypy3.8)	3m 1s
test (windows-2022, pypy3.9)	2m 38s
test (windows-2022, pypy3.10)	5m 14s
builder_pypandoc	9s
builder_pypandoc_binary (macos-14)	53s
builder_pypandoc_binary (windows-2022)	1m 43s
builder_pypandoc_binary (ubuntu-22.04)	4m 58s
publisher_release	0s
publisher_latest	0s
	1h 18m 46s

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