Remove nlow and nhigh parameters from outlier_detection

[stscijgbot-jp]

Issue JP-3705 was created on JIRA by Misty Cracraft:

The parameters 'nlow' and 'nhigh' have been deprecated from the outlier_detection step in the pipeline, but could not be removed from the code until the parameter reference files no longer contained these parameters.

The MIRI outlier_detection parameter reference files have just finished removing these parameters from the reference files. No other instruments seem to use these parameters in their reference files.

[stscijgbot-jp]

Comment by Ned Molter on JIRA:

Fixed by #8870