Modify mixing elbow example input files to ensure boundary conditions setup correctly

### 🔍 Before submitting the issue

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

### 🐞 Description of the bug

Inlets need labelling corrected to ensure two separate boundary conditions are created.

### 📝 Steps to reproduce

Run mixing elbow example and two inlets are combined as a single boundary condition

### 💻 Which operating system are you using?

Windows

### 📀 Which ANSYS version are you using?

NA

### 🐍 Which Python version are you using?

3.7

### 📦 Installed packages

```shell
NA
```