docs: Document disabling unattended-upgrades.
docs: Document disabling unattended-upgrades.

I don't think this is exactly the right place to document this, but
I'm not sure there's a better one without some restructuring this page
in general (which would probably have value).

Fixes #8769.

rht/zulip,rishig/zulip,brainwane/zulip,zulip/zulip,zulip/zulip,hackerkid/zulip,jackrzhang/zulip,timabbott/zulip,zulip/zulip,andersk/zulip,shubhamdhama/zulip,rht/zulip,hackerkid/zulip,kou/zulip,dhcrzf/zulip,dhcrzf/zulip,andersk/zulip,timabbott/zulip,showell/zulip,rishig/zulip,kou/zulip,kou/zulip,dhcrzf/zulip,tommyip/zulip,timabbott/zulip,synicalsyntax/zulip,andersk/zulip,rht/zulip,zulip/zulip,hackerkid/zulip,punchagan/zulip,andersk/zulip,zulip/zulip,brainwane/zulip,rht/zulip,rishig/zulip,hackerkid/zulip,rishig/zulip,brainwane/zulip,jackrzhang/zulip,eeshangarg/zulip,hackerkid/zulip,andersk/zulip,brainwane/zulip,rishig/zulip,tommyip/zulip,showell/zulip,hackerkid/zulip,kou/zulip,rishig/zulip,showell/zulip,tommyip/zulip,brainwane/zulip,showell/zulip,timabbott/zulip,showell/zulip,andersk/zulip,punchagan/zulip,kou/zulip,shubhamdhama/zulip,eeshangarg/zulip,tommyip/zulip,shubhamdhama/zulip,shubhamdhama/zulip,tommyip/zulip,punchagan/zulip,eeshangarg/zulip,eeshangarg/zulip,eeshangarg/zulip,timabbott/zulip,punchagan/zulip,synicalsyntax/zulip,hackerkid/zulip,dhcrzf/zulip,jackrzhang/zulip,jackrzhang/zulip,rht/zulip,zulip/zulip,synicalsyntax/zulip,dhcrzf/zulip,showell/zulip,dhcrzf/zulip,punchagan/zulip,brainwane/zulip,dhcrzf/zulip,shubhamdhama/zulip,kou/zulip,timabbott/zulip,synicalsyntax/zulip,synicalsyntax/zulip,andersk/zulip,punchagan/zulip,zulip/zulip,rishig/zulip,kou/zulip,jackrzhang/zulip,rht/zulip,jackrzhang/zulip,eeshangarg/zulip,synicalsyntax/zulip,punchagan/zulip,synicalsyntax/zulip,eeshangarg/zulip,jackrzhang/zulip,showell/zulip,timabbott/zulip,tommyip/zulip,shubhamdhama/zulip,shubhamdhama/zulip,brainwane/zulip,tommyip/zulip,rht/zulip