maint: don't emit an extra newline in each of two diagnostics

maint: don't emit an extra newline in each of two diagnostics

* src/shuf.c (main): Remove a stray newline in a diagnostic.
* src/od.c (main): Likewise.
Detected via these:
  git grep -A1 'error *(.*,$' | grep -C1 '\\n"[,)]'
  git grep 'error *(.*;$' | grep '\\n"[,)]'