Fix/translatable strings in theme json #12865

Job	Run time
Core running from build / Core running from build / Linux	2m 5s
Core running from build / Core running from build / MacOS	1m 42s
Core running from src / Core running from src / Linux	2m 2s
Core running from build / Core running from build / Windows	3m 47s
Core running from src / Core running from src / Windows	3m 45s
Core running from src / Core running from src / MacOS	1m 57s
Gutenberg running from build / Gutenberg running from build / Linux	8m 58s
Gutenberg running from src / Gutenberg running from src / Linux	8m 44s
Gutenberg running from build / Gutenberg running from build / Windows	12m 22s
Gutenberg running from src / Gutenberg running from src / Windows	12m 9s
Gutenberg running from src / Gutenberg running from src / MacOS	7m 52s
Gutenberg running from build / Gutenberg running from build / MacOS	9m 28s
Slack Notifications	0s
Failed workflow tasks	0s
	1h 14m 51s

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