[circt] Remove deprecated dedup option (#3634)

Remove the deprecated -dedup option.  This was deprecated in firtool
1.57.0 and is planned to be removed soon.  This option has no effect.
Deduplication always runs.

See: https://github.com/llvm/circt/pull/6191



Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>