Use conf TICKET_MESSAGE_MAIL_INTRO instead of translation key #4

Job	Run time
gh-travis	0s
pre-commit / pre-commit	2m 26s
phan / Run phan	3m 14s
windows-ci / win-test (windows-latest, 7.4)	8m 32s
phpstan / php-stan (8.2)	13m 26s
	27m 38s

Provide feedback