Remove np.nan assignment to uint array and remove unneeded uint32 conversion

A bug was discovered during deployment of 3.6.0 when LPD dark tries to assign np.nan to uint32 array.

Description

1. Remove np.nan element assignment. No clear reason why this is needed for plotting.
2. Remove unneeded data conversion for the badpixels constants.
3. Refactor the lines of code where old badpixels constant are data converted to uint32

How Has This Been Tested?

Tested against the reference dark runs 145, 146, 147

Relevant Documents (optional)

LPD_DARK_EXAMPLE.pdf

Types of changes

Checklist:

Reviewers

@schmidtp @kluyvert @danilevc