Delete old marine DA scripts

[guillaumevernieres]

Thank you @guillaumevernieres for the approval. Any thoughts on how to handle the scratch2 reference in ./ush/ufsda/yamltools.py? Below is one option

One option for ./ush/ufsda/yamltools.py is to delete it along with the script that calls it, scripts/old/exgdas_global_marine_analysis_prep.py. If we delete scripts/old/exgdas_global_marine_analysis_prep.py, we should consider removing the entire directory scripts/old.

Originally posted by @RussTreadon-NOAA in #1835 (comment)