Editor: Ignore built assets introduced in WordPress 6.9, SVN edition.

Update the `svn:ignore` property for newly introduced assets in the `src/wp-includes/blocks` directory. 

The code run for this commit was:

{{{
cd src/wp-includes/blocks
svn propset svn:ignore '*.js.map
*.js
*.css' . --recursive
}}}

Follow up to [61012].

See #64117.


git-svn-id: https://develop.svn.wordpress.org/trunk@61042 602fd350-edb4-49c9-b593-d223f7449a82

Author: peterwilsoncc