settings: Fix buggy emoji format loading spinner.
settings: Fix buggy emoji format loading spinner.

When a user clicked the current emoji format in "display settings",
we'd show an infinite loading spinner (basically as a side effect of
trying to tell the server to change the emoji format to what it
already was).

Fix this by aborting early if the emoji format is already the option
that the user clicked.

Fixes #13684.

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