Expire silences after one day instead of one year

[haasad]

The cronjob renews the silence every 4 hours. I don't see any added benefits in creating silences with 1 year lifetime instead of one day.

However there is one major downside. If the silence functionality is used to suppress certain alerts temporarily, the silence stays active for 1 year after it's removed from the config hierarchy. To enable the alert again it, the silence has to be expired manually on all clusters.

Reducing this to one day is a compromise that allows to remove silences and ensure they're active again in a reasonable timeframe without having to manually expire all silences. Happy to discuss other values for the duration.

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[simu]

LGTM. Probably needs a make gen-golden-all

[haasad]

make gen-golden-all is still running 🐌 😄