lint: Fix errors with stats.js with new eslint.
lint: Fix errors with stats.js with new eslint.

This (for ... in) syntax we shouldn't be using anyway, but this at
least fixes the worst aspect of it.

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