Bump alpine from 3.20.3 to 3.21.0 in /newrelic-daemon #120

Job	Run time
Build and push PHP 7.4	3m 59s
Build and push nginx	19s
Build and push PHP 8.0	4m 44s
Build and push nginx-proxy	20s
Build and push PHP 8.1	5m 10s
Build and push postfix	2m 38s
Build and push PHP 8.2	4m 57s
Build and push redis	26s
Build and push PHP 8.3	5m 11s
Build and push cron	23s
Build and push PHP 8.4	4m 59s
Build and push mailhog	23s
Build and push mariadb	27s
Build and push newrelic-daemon	21s
	34m 17s

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