Don't prepare the response body for HEAD requests #12990

Job	Run time
Core running from build / Core running from build / Linux	2m 14s
Core running from src / Core running from src / Linux	2m 7s
Core running from build / Core running from build / Windows	4m 6s
Core running from src / Core running from src / Windows	3m 55s
Core running from build / Core running from build / MacOS	2m 35s
Core running from src / Core running from src / MacOS	1m 53s
Gutenberg running from build / Gutenberg running from build / Linux	8m 49s
Gutenberg running from src / Gutenberg running from src / Linux	9m 10s
Gutenberg running from build / Gutenberg running from build / Windows	11m 45s
Gutenberg running from src / Gutenberg running from src / Windows	11m 57s
Gutenberg running from build / Gutenberg running from build / MacOS	9m 18s
Gutenberg running from src / Gutenberg running from src / MacOS	10m 46s
Slack Notifications	0s
Failed workflow tasks	0s
	1h 18m 35s

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