pdiff: drop unnecessary CLI options

8 jobs for topic/default/pdiff-help in 7 minutes and 6 seconds (queued for 1 second)
Status Name Job ID Coverage
  Test
passed checks-py2 #168966

00:03:21

passed checks-py3 #168967

00:01:02

passed doc #168972

00:00:28

manual pytype #168965
allowed to fail manual
passed tests-py2-cext #168968

00:03:05

passed tests-py2-pure #168969

00:06:55

passed tests-py3-cext #168970

00:07:04

passed tests-py3-pure #168971

00:02:12