deps: delete deps/icu-small/source/io

The previous commit removed the dependency on the code in that directory. This commit removes the directory itself and shrinks the source tarball by about 200 kB. PR-URL: #13656 Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Refael Ackermann <[email protected]>

Author: bnoordhuis