Follow-up: Add wp_is_valid_utf8() for normalizing UTF-8 checks.
wp_is_valid_utf8()
When the seemsUtf8 test file was removed, the file was left in subversion as an empty file. This patch removes the file.
seemsUtf8
Discussed in https://core.trac.wordpress.org/ticket/38044
Follow-up to [60630].
Props dmsnell, johnbillion. See #38044.