Fix naive filtering of uploads directory. #3797

Job	Run time
Core running from build / Core running from build / Linux	2m 12s
Core running from src / Core running from src / Linux	1m 53s
Core running from build / Core running from build / Windows	3m 5s
Core running from src / Core running from src / Windows	3m 36s
Core running from build / Core running from build / MacOS	3m 15s
Core running from src / Core running from src / MacOS	3m 23s
Gutenberg running from build / Gutenberg running from build / Linux	8m 13s
Gutenberg running from src / Gutenberg running from src / Linux	8m 0s
Gutenberg running from build / Gutenberg running from build / Windows	11m 10s
Gutenberg running from src / Gutenberg running from src / Windows	11m 52s
Gutenberg running from build / Gutenberg running from build / MacOS	12m 23s
Gutenberg running from src / Gutenberg running from src / MacOS	14m 1s
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	1h 23m 5s

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