Update More block description

[Soean]

Description

Updates the description of the More block.
Fixes: #11458

Old:
Want to show only an excerpt of this post on your home page? Use this block to define where you want the separation.
New:
Mark the excerpt of this content. Content before this block will be shown in the excerpt on your archives page.

[gziolo]

It changes more than home page to homepage. @alexislloyd what's your take on the proposed change? It looks like you iterated on it a bit earlier, so I would expect this PR to be scoped to only fix the way home page is used.

[swissspidy]

Only fixing homepage everywhere in a more scoped fashion makes sense.

We can then improve the text in a separate PR. Could we then get rid of the "post" bit of the description as well please? Otherwise it's not accurate for other post types. I would replace it with "content".

[tofumatt]

I don't like block descriptions that lead with questions. We use an entire sentence to ask the user if this is the block they want to be using before telling them what it does; the question is an indirect way of asking them and I don't think it's very instructive 😄

[gziolo]

I updated home page with homepage with #11661 to land it in 4.3 and resolve the original issue. Feel free to continue discussion on the improvements to this description without the pressure of time :)

[tofumatt]

Looks good, I say