Fix sunday cronjob

[casperklein]

Description

#1788 introduced an error: BusyBox crond does not support 7 for Sundays. Changing it to 0 fixes the issue.

Before:

d6063bb15688:/# crond -f -d 8
crond: crond (busybox 1.36.1) started, log level 8
crond: user root: parse error at 7

After:

d6063bb15688:/# vi /var/spool/cron/crontabs/root # replace 7 with 0
d6063bb15688:/# crond -f -d 8
crond: crond (busybox 1.36.1) started, log level 8

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.