Fix assumption that download URLs contain file extension #3590

Job	Run time
Diagnostic export (macos-latest, linked)	1m 19s
Diagnostic export (ubuntu-latest, linked)	1m 12s
Diagnostic export (ubuntu-latest, nightly-latest)	25s
Diagnostic export (windows-latest, linked)	3m 37s
Diagnostic export (macos-latest, nightly-latest)	1m 29s
Diagnostic export (windows-latest, nightly-latest)	4m 52s
	12m 54s

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