fix(fmt): return `None` if sql fmt result is the same (#27014)
Similar with https://github.com/denoland/deno/pull/25848, we need to
make `format_sql` to return `None` so we do not flag well formatted sql
files as being wrong.
Signed-off-by: m4rc3l05 <15786310+M4RC3L05@users.noreply.github.com>
