dmUpdate: Fix so that filenames are not saved in lowercase

[uramirez8707]

Description Removes the lowercase when saving the filenames into the sorted list of files. This sorted list is used to find the file_ids of the variables when the variable is registered using a binary search (for performance). The filename should be saved as it is saved in the yaml object.

Without this change, we are getting errors such as /gpfs/f5/gfdl_f/scratch/Niki.Zadeh/FMS2024.01-beta1_mom6_20231130_ymal_1/OM4p5_CORE2_IAF_COBALT4.0_abio_csf_mle200/ncrc5.intel23-pr od/stdout/run/OM4p5_CORE2_IAF_COBALT4.0_abio_csf_mle200_1x1m0d_1057x1o1.o134750073

It is still needed for the variables: https://github.com/NOAA-GFDL/FMS/pull/1176#discussion_r1173911530

Fixes # (issue)

How Has This Been Tested? CI

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] Any dependent changes have been merged and published in downstream modules
• [x] New check tests, if applicable, are included
• [x] make distcheck passes