typing_notifications: Show several users are typing if num of typists > 3.
typing_notifications: Show several users are typing if num of typists > 3.

I believe we intended to show 'several users are typing...' only
if number of typists are more than 3 but not 2.

The variable name MAX_USERS_TO_DISPLAY_NAME and commit message of
dba21d201c183d0b461297975bcd4a3990a43526 which added this also
suggests the same.

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