Don't prepare the response body for HEAD requests #12944

Job	Run time
Core running from build / Core running from build / MacOS	2m 50s
Core running from src / Core running from src / MacOS	2m 48s
Core running from build / Core running from build / Linux	2m 7s
Core running from src / Core running from src / Linux	1m 58s
Core running from build / Core running from build / Windows	3m 45s
Core running from src / Core running from src / Windows	3m 46s
Gutenberg running from build / Gutenberg running from build / Linux	8m 47s
Gutenberg running from src / Gutenberg running from src / Linux	8m 41s
Gutenberg running from build / Gutenberg running from build / Windows	10m 31s
Gutenberg running from src / Gutenberg running from src / Windows	10m 31s
Gutenberg running from build / Gutenberg running from build / MacOS	9m 11s
Gutenberg running from src / Gutenberg running from src / MacOS	10m 5s
Slack Notifications	1s
Failed workflow tasks	1s
	1h 15m 2s

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