refactor: Remove obsolete .hidden-filter.
refactor: Remove obsolete .hidden-filter.

This is an obsolete css class in left-sidebar.css.

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