While adding a new reaction, we create a new JQuery element
called "message_reaction_container" and append it to the
view to display the emoji.
Previously, when the reaction count became zero for an emoji,
we used to just remove the emoji but not the JQuery element
mentioned above, requiring a reload to remove it. This
inconsistency introduced a bug in the UI. causing unwanted
spaces between emojies as this element used to get accumulated.
This commit resolves the bug by introducing logic to remove
reaction containers with no reactions.
Fixes: #32983