bots: Add linter rule to prevent open() calls.
bots: Add linter rule to prevent open() calls.

Addresses #5395.

timabbott/zulip,jrowan/zulip,andersk/zulip,timabbott/zulip,tommyip/zulip,amanharitsh123/zulip,vabs22/zulip,hackerkid/zulip,Galexrt/zulip,kou/zulip,andersk/zulip,mahim97/zulip,tommyip/zulip,eeshangarg/zulip,eeshangarg/zulip,Galexrt/zulip,brockwhittaker/zulip,shubhamdhama/zulip,showell/zulip,dhcrzf/zulip,tommyip/zulip,mahim97/zulip,vaidap/zulip,timabbott/zulip,brockwhittaker/zulip,synicalsyntax/zulip,jackrzhang/zulip,mahim97/zulip,kou/zulip,mahim97/zulip,brockwhittaker/zulip,vaidap/zulip,zulip/zulip,synicalsyntax/zulip,jrowan/zulip,verma-varsha/zulip,dhcrzf/zulip,brainwane/zulip,brainwane/zulip,punchagan/zulip,hackerkid/zulip,eeshangarg/zulip,kou/zulip,mahim97/zulip,andersk/zulip,punchagan/zulip,verma-varsha/zulip,jackrzhang/zulip,amanharitsh123/zulip,jrowan/zulip,Galexrt/zulip,eeshangarg/zulip,hackerkid/zulip,amanharitsh123/zulip,brainwane/zulip,rishig/zulip,synicalsyntax/zulip,vabs22/zulip,shubhamdhama/zulip,hackerkid/zulip,rht/zulip,rishig/zulip,showell/zulip,synicalsyntax/zulip,Galexrt/zulip,shubhamdhama/zulip,vaidap/zulip,rht/zulip,jrowan/zulip,zulip/zulip,jrowan/zulip,vabs22/zulip,shubhamdhama/zulip,brockwhittaker/zulip,vaidap/zulip,vabs22/zulip,rishig/zulip,jackrzhang/zulip,zulip/zulip,vabs22/zulip,eeshangarg/zulip,eeshangarg/zulip,Galexrt/zulip,showell/zulip,kou/zulip,dhcrzf/zulip,rht/zulip,tommyip/zulip,eeshangarg/zulip,rishig/zulip,kou/zulip,andersk/zulip,dhcrzf/zulip,brainwane/zulip,jackrzhang/zulip,brainwane/zulip,rht/zulip,punchagan/zulip,verma-varsha/zulip,rishig/zulip,verma-varsha/zulip,amanharitsh123/zulip,dhcrzf/zulip,hackerkid/zulip,andersk/zulip,andersk/zulip,andersk/zulip,jackrzhang/zulip,verma-varsha/zulip,zulip/zulip,timabbott/zulip,punchagan/zulip,kou/zulip,Galexrt/zulip,punchagan/zulip,vaidap/zulip,mahim97/zulip,jrowan/zulip,rht/zulip,brainwane/zulip,amanharitsh123/zulip,zulip/zulip,dhcrzf/zulip,verma-varsha/zulip,rishig/zulip,showell/zulip,brockwhittaker/zulip,synicalsyntax/zulip,rht/zulip,jackrzhang/zulip,Galexrt/zulip,showell/zulip,timabbott/zulip,timabbott/zulip,dhcrzf/zulip,shubhamdhama/zulip,timabbott/zulip,shubhamdhama/zulip,brockwhittaker/zulip,kou/zulip,tommyip/zulip,zulip/zulip,hackerkid/zulip,synicalsyntax/zulip,showell/zulip,showell/zulip,shubhamdhama/zulip,vabs22/zulip,rishig/zulip,amanharitsh123/zulip,synicalsyntax/zulip,vaidap/zulip,punchagan/zulip,zulip/zulip,punchagan/zulip,brainwane/zulip,jackrzhang/zulip,tommyip/zulip,rht/zulip,tommyip/zulip,hackerkid/zulip