minor: stellar polarization primitives don't need to hard-code the FPM radii since they're in the constants file.

[dsavransky]

Noticed while working with Li-Wei. The gpi_subtract_mean_stellar_polarization_podc.pro primitive has all the FPM radii hard coded in the primitive source. These values are actually all available in pipeline_constants in the config directory (e.g. "gpi_get_constant('fpm_diam_h')") There's no chance these are changing any time soon, but the general principle of "avoid writing down the same information in multiple places" says the primitive should use the config file rather than having its own lookup table.

Lowest possible priority on this one. This is sort of just an FYI that those values do exist in the constants file.

[dsavransky]

Recovering rm journals for issue:

kfollette: Punting on this one since it's a low priority.