node tests: Fix schema for stream events.
node tests: Fix schema for stream events.

hackerkid/zulip,rht/zulip,rht/zulip,eeshangarg/zulip,eeshangarg/zulip,rht/zulip,punchagan/zulip,zulip/zulip,showell/zulip,eeshangarg/zulip,hackerkid/zulip,hackerkid/zulip,eeshangarg/zulip,andersk/zulip,showell/zulip,andersk/zulip,zulip/zulip,kou/zulip,kou/zulip,showell/zulip,eeshangarg/zulip,kou/zulip,showell/zulip,brainwane/zulip,brainwane/zulip,andersk/zulip,kou/zulip,zulip/zulip,rht/zulip,zulip/zulip,kou/zulip,brainwane/zulip,punchagan/zulip,andersk/zulip,punchagan/zulip,showell/zulip,hackerkid/zulip,punchagan/zulip,hackerkid/zulip,andersk/zulip,zulip/zulip,eeshangarg/zulip,rht/zulip,zulip/zulip,andersk/zulip,punchagan/zulip,rht/zulip,zulip/zulip,brainwane/zulip,hackerkid/zulip,showell/zulip,showell/zulip,kou/zulip,brainwane/zulip,kou/zulip,brainwane/zulip,andersk/zulip,punchagan/zulip,eeshangarg/zulip,punchagan/zulip,rht/zulip,hackerkid/zulip,brainwane/zulip