[Do not merge] Specify `Accept` header for `toolcache.downloadTool` #5103

Job	Run time
Config export (macos-latest, nightly-latest)	3m 3s
Config export (ubuntu-latest, nightly-latest)	1m 4s
Config export (windows-latest, linked)	2m 4s
Config export (macos-latest, linked)	1m 7s
Config export (windows-latest, nightly-latest)	2m 48s
Config export (ubuntu-latest, linked)	1m 13s
	11m 19s

Provide feedback