Use a raw F string for regex in pandoc downloader #266

Job	Run time
test (ubuntu-20.04, 3.7)	35s
test (ubuntu-20.04, 3.8)	29s
test (ubuntu-20.04, 3.9)	27s
test (ubuntu-20.04, 3.10)	32s
test (ubuntu-20.04, 3.11)	24s
test (ubuntu-20.04, 3.12)	27s
test (ubuntu-20.04, pypy3.8)	1m 14s
test (ubuntu-20.04, pypy3.9)	40s
test (ubuntu-20.04, pypy3.10)	42s
test (ubuntu-22.04, 3.7)	46s
test (ubuntu-22.04, 3.8)	29s
test (ubuntu-22.04, 3.9)	30s
test (ubuntu-22.04, 3.10)	26s
test (ubuntu-22.04, 3.11)	30s
test (ubuntu-22.04, 3.12)	29s
test (ubuntu-22.04, pypy3.8)	1m 42s
test (ubuntu-22.04, pypy3.9)	49s
test (ubuntu-22.04, pypy3.10)	50s
test (macos-13, 3.7)	1m 34s
test (macos-13, 3.8)	1m 2s
test (macos-13, 3.9)	51s
test (macos-13, 3.10)	57s
test (macos-13, 3.11)	1m 7s
test (macos-13, 3.12)	58s
test (macos-13, pypy3.8)	1m 13s
test (macos-13, pypy3.9)	1m 1s
test (macos-13, pypy3.10)	1m 9s
test (windows-2022, 3.7)	1m 25s
test (windows-2022, 3.8)	2m 3s
test (windows-2022, 3.9)	1m 49s
test (windows-2022, 3.10)	2m 1s
test (windows-2022, 3.11)	1m 24s
test (windows-2022, 3.12)	2m 1s
test (windows-2022, pypy3.8)	2m 15s
test (windows-2022, pypy3.9)	2m 33s
test (windows-2022, pypy3.10)	2m 45s
builder_pypandoc	9s
builder_pypandoc_binary (macos-14)	41s
builder_pypandoc_binary (windows-2022)	1m 34s
builder_pypandoc_binary (ubuntu-22.04)	4m 30s
publisher_latest	0s
publisher_release	0s
	47m 3s

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