datetime: grayout automatic timezone

Automatic timezone does not work if location sharing is disabled in privacy.

Grays out automatic timezone setting if location sharing is disabled in privacy
settings. Enable automatic timezone seting if location sharing is enabled.

https://bugzilla.gnome.org/show_bug.cgi?id=788714
11 jobs for master in 3 minutes and 59 seconds (queued for 2 minutes and 16 seconds)
Status Job ID Name Coverage
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