Move NEWS entries out of directories with spaces (GH-127067)

Cleanup after GH-126063, including moving the `README.rst` files to the new directories.

diff --git a/Misc/NEWS.d/next/C API/2024-07-03-13-39-13.gh-issue-121058.MKi1MV.rst b/Misc/NEWS.d/next/C_API/2024-07-03-13-39-13.gh-issue-121058.MKi1MV.rst
similarity index 100%
rename from Misc/NEWS.d/next/C API/2024-07-03-13-39-13.gh-issue-121058.MKi1MV.rst
rename to Misc/NEWS.d/next/C_API/2024-07-03-13-39-13.gh-issue-121058.MKi1MV.rst

diff --git a/Misc/NEWS.d/next/C API/README.rst b/Misc/NEWS.d/next/C_API/README.rst
similarity index 100%
rename from Misc/NEWS.d/next/C API/README.rst
rename to Misc/NEWS.d/next/C_API/README.rst

diff --git a/Misc/NEWS.d/next/Core and Builtins/README.rst b/Misc/NEWS.d/next/Core_and_Builtins/README.rst
similarity index 100%
rename from Misc/NEWS.d/next/Core and Builtins/README.rst
rename to Misc/NEWS.d/next/Core_and_Builtins/README.rst