message_edit_form: Change class name of stream select element.
message_edit_form: Change class name of stream select element.

We set the class name to be same as the one used in move topic
to stream popover so that a single class can be used to control
the look of both dropdowns.

eeshangarg/zulip,eeshangarg/zulip,zulip/zulip,andersk/zulip,rht/zulip,kou/zulip,zulip/zulip,rht/zulip,eeshangarg/zulip,andersk/zulip,zulip/zulip,andersk/zulip,eeshangarg/zulip,kou/zulip,rht/zulip,rht/zulip,andersk/zulip,andersk/zulip,kou/zulip,rht/zulip,kou/zulip,rht/zulip,zulip/zulip,kou/zulip,eeshangarg/zulip,kou/zulip,kou/zulip,zulip/zulip,eeshangarg/zulip,eeshangarg/zulip,zulip/zulip,rht/zulip,zulip/zulip,andersk/zulip,andersk/zulip