Use lower-case for replaceable elements

### 📝 Description of the feature

This issue is to keep a track of a question raised in https://github.com/ansys/pymapdl/pull/3750/files#r2052420475.
Should the ``replaceable`` elements be modified into lower-case text?

This will be checked after the first integration to PyMAPDL.

### 💡 Steps for implementing the feature

_No response_

### 🔗 Useful links and references

_No response_

Review the linked PyMAPDL pull-request discussion first, then inspect how the converter handles replaceable elements during the first PyMAPDL integration. The issue names no file, entry point, test, or concrete implementation steps; done requires resolving whether lower-case output is wanted and recording or implementing that decision.

Written by the indexing model from the issue text.