streams: Remove subs.show_and_focus_on_narrow().
streams: Remove subs.show_and_focus_on_narrow().

We stopped calling this in this commit:

    3d77aa49db3492f26accabda95cb84c3ae0069ce

We also remove its helper function and the obsolete
event that only it was looking for.

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