Don't prepare the response body for HEAD requests #12905

Job	Run time
Core running from build / Core running from build / Linux	2m 12s
Core running from src / Core running from src / Linux	1m 58s
Core running from build / Core running from build / Windows	4m 21s
Core running from src / Core running from src / Windows	3m 15s
Core running from build / Core running from build / MacOS	3m 1s
Core running from src / Core running from src / MacOS	1m 51s
Gutenberg running from build / Gutenberg running from build / Linux	8m 32s
Gutenberg running from src / Gutenberg running from src / Linux	8m 31s
Gutenberg running from build / Gutenberg running from build / Windows	11m 42s
Gutenberg running from src / Gutenberg running from src / Windows	12m 18s
Gutenberg running from build / Gutenberg running from build / MacOS	7m 55s
Gutenberg running from src / Gutenberg running from src / MacOS	8m 41s
Slack Notifications	0s
Failed workflow tasks	0s
	1h 14m 17s

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