Provide `Authorization` header when downloading `update-job-proxy` #5149

Job	Run time
Diagnostic export (macos-latest, nightly-latest)	1m 25s
Diagnostic export (ubuntu-latest, nightly-latest)	1m 1s
Diagnostic export (windows-latest, nightly-latest)	2m 26s
Diagnostic export (windows-latest, linked)	3m 57s
Diagnostic export (macos-latest, linked)	1m 5s
Diagnostic export (ubuntu-latest, linked)	59s
	10m 53s

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