Ansys.Edb.Core.DataBase.add_variable method doe not take parameter variable

### 🔍 Before submitting the issue

- [x] I have searched among the existing issues
- [x] I am using a Python virtual environment

### 🐞 Description of the bug

When setting a project variable setting this one to parameter does not create the varaible

### 📝 Steps to reproduce

Use pyedb system test. NEbale grpc use-grpc -> force as True in conftest.py

file test_edb_modeler.py -> test_duplicate
``` python

edbapp = edb_examples.create_empty_edb()
edbapp["$H"] = "0.65mil"
assert edbapp["$H"] == 1.651e-5

```
you will see with debugging and step into:
self.active_db.add_variable(variable_name, variable_value, is_param=is_parameter)
if is_param=True
get_all_variable_names() returns an empty list
while set to False

### 💻 Which operating system are you using?

Windows

### 📀 Which ANSYS version are you using?

NA

### 🐍 Which Python version are you using?

3.9

### 📦 Installed packages

```shell
NA
```