Followup f002aa4022
We are renaming `discourse_reactions_experimental_allow_any_emoji` to
`discourse_reactions_allow_any_emoji`
and moving it out of the Experimental site setting area.
We originally kept this setting experimental because we thought
there might besome moderation concerts around allowing any emoji to be
used.
However, we later realised the `emoji_deny_list` core site setting can
be used to effectively restrict which emoji are allowed to be used here.
The setting `discourse_reactions_allow_any_emoji` remains off by
default.
I also added some of the discourse-reactions settings to the `emojis`
site setting area to make them easier to find.