The "filter" should only be set for raw ccds and not for raw amps in obs_lsst

With https://rubinobs.atlassian.net/browse/DM-21048#icft=DM-21048 it is possible to read in raw data even when the filter is not listed in the obs package, although a warning is given. This can be annoying because currently a warning is given for each amplifier, although it is unnecessary to set/check the filter when reading in amps, it only needs to be done (and is done!) when assembling the ccd.

It appears as though the place to put the change is in https://github.com/lsst/obs_lsst/blob/aeaebe9ad92137ac7a57e2bd580746e2cbffe16f/python/lsst/obs/lsst/lsstCamMapper.py#L393 where the call to self._standardizeExposure should have filter=False.