Don't prepare the response body for HEAD requests #12978

Job	Run time
Core running from build / Core running from build / Linux	32s
Core running from src / Core running from src / Linux	31s
Core running from build / Core running from build / Windows	17s
Core running from src / Core running from src / Windows	23s
Core running from build / Core running from build / MacOS	2m 20s
Core running from src / Core running from src / MacOS	32s
Gutenberg running from build / Gutenberg running from build / Linux	31s
Gutenberg running from src / Gutenberg running from src / Linux	31s
Gutenberg running from build / Gutenberg running from build / Windows	1m 50s
Gutenberg running from src / Gutenberg running from src / Windows	21s
Gutenberg running from build / Gutenberg running from build / MacOS	20s
Gutenberg running from src / Gutenberg running from src / MacOS	19s
Slack Notifications	1s
Failed workflow tasks	1s
	8m 29s

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