gitlab: Document the local network security setting.
gitlab: Document the local network security setting.

This should help users debug issues with the GitLab webhook not
working with recent GitLab releases.

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