Don't prepare the response body for HEAD requests #12974

Job	Run time
Core running from build / Core running from build / Linux	2m 20s
Core running from src / Core running from src / Linux	1m 59s
Core running from build / Core running from build / Windows	3m 49s
Core running from src / Core running from src / Windows	4m 10s
Core running from build / Core running from build / MacOS	2m 47s
Core running from src / Core running from src / MacOS	1m 48s
Gutenberg running from build / Gutenberg running from build / Linux	8m 53s
Gutenberg running from src / Gutenberg running from src / Linux	8m 40s
Gutenberg running from src / Gutenberg running from src / Windows	11m 45s
Gutenberg running from build / Gutenberg running from build / Windows	12m 33s
Gutenberg running from build / Gutenberg running from build / MacOS	8m 20s
Gutenberg running from src / Gutenberg running from src / MacOS	12m 26s
Slack Notifications	0s
Failed workflow tasks	0s
	1h 19m 30s

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