docs: Explain options for preventing changes during export.
docs: Explain options for preventing changes during export.

This makes it a bit clearer that one doesn't need to deactivate a
realm just to export data.

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