Fix assumption that download URLs contain file extension #3594

Job	Run time
Diagnostic export (macos-latest, linked)	1m 24s
Diagnostic export (macos-latest, nightly-latest)	1m 22s
Diagnostic export (ubuntu-latest, nightly-latest)	57s
Diagnostic export (windows-latest, nightly-latest)	4m 27s
Diagnostic export (ubuntu-latest, linked)	59s
Diagnostic export (windows-latest, linked)	3m 14s
	12m 23s

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