Move misplaced blurb entries

[Yhg1s]

Move misplaced blurb entries from "C_API" to "C API", and from "Core_and_Builtins" to "Core and Builtins".

[ambv]

Shouldn't this rename go the other way?

[hugovk]

Blurb <= 1.1.0 wants the old names with spaces.

• https://github.com/python/release-tools currently uses 1.1.0

Blurb >= 1.2.0 can read directories both with spaces and with underscores.

• python/release-tools#143 upgrades to use 1.2.0

If we merge that PR, we can close (or merge!) this PR.

If @Yhg1s wants to do it the old way for this release, let's merge this one.

[ambv]

I merged the release-tools PR.

[Yhg1s]

I already fixed this for 3.13.0b4 in a separate PR. I sent this PR to Hugo because this is his bailiwick now :)

[hugovk]

Thanks! Let's leave it as is, new blurb can read from both.

After today's release is out, we can also merge python/blurb_it#332 and I'll post on Discuss to encourage people to upgrade their blurb CLI. Further down the line, we can add a pre-commit check to prevent creation of dirs with spaces.