Make collapsed notes subscribe to stream

What does this MR do?

Previously, when the note was collapsed, it didn't get updates such as reactions from streaming server. This was a problem, as any change made to the post before it got uncollapsed would end up being ignored (as the post wasn't listening to them).

For example, consider a stream that looks like this.

o @someone: message A [a collapsed reply using "Collapse replies replied to" option]
|
/\ someone
\/ @someone
message B

-----

/\  someone
\/ @someone
message A

If message A at the bottom gets reacted to, and then a collapsed reply is viewed, it won't have a reaction.

This is fixed by using v-show rather than v-if to make sure the streaming server is notified early about post being visible.

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