test_unread: Remove test for removed mobile hack.
test_unread: Remove test for removed mobile hack.

This should have been included in
731cd794361ca94b7062ce155b76a58a0b5d5fd6.

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