Hotfix: Allow certain case parameters to be analytic expressions again

Description

After addressing GH-424, I broke parameters like those found in 1D_shuosher and 1D_titarevtorro which have analytic values -- they were falsely rejected as "strings" when they should have been accepted.

Type of change

Please delete options that are not relevant.

[x] Bug fix (non-breaking change which fixes an issue)

Scope

[x] This PR comprises a set of related changes with a common goal

If you cannot check the above box, please split your PR into multiple PRs that each have a common goal.

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

[x] ./mfc.sh test passes
[x] Ran 1D_shuosher -- Simulation ran to completion
[x] Ran 1D_titarevtorro -- Case file passed validation but preprocessing failed:

 Pre-processing a 999x0x0 case on 1 rank(s)
 Processing patch           1
 Processing patch           2
 Invalid hcid specified for patch 2
STOP 1

This is behavior also appears on v4.8.2, before the new case validation was implemented. This may be specific to my machine.

Test Configuration:

What computers and compilers did you use to test this: Personal laptop. GNU:
AMD Ryzen 7840U -- 8 Core, 16 Thread
32 GB DDR5

Checklist

[ ] I have added comments for the new code
[ ] I ran ./mfc.sh format before committing my code
[ ] New and existing tests pass locally with my changes, including with GPU capability enabled (both NVIDIA hardware with NVHPC compilers and AMD hardware with CRAY compilers) and disabled
[ ] This PR does not introduce any repeated code (it follows the DRY principle)
[ ] I cannot think of a way to condense this code and reduce any introduced additional line count

MFlowCode / MFC