Plot Nodal stress Error

### 🔍 Before submitting the issue

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

### 🐞 Description of the bug

mapdl.post_processing.nodal_eqv_stress()


### 📝 Steps to reproduce

When I am trying to plot Nodal Stress using the commands: "result.plot_nodal_stress(0)" or "mapdl.post_processing.nodal_eqv_stress()"
it gives me the following Error.!

ERROR: CRITICAL - - logging - handle_exception - Uncaught exception
Traceback (most recent call last):
File "C:\Users\dell\PycharmProjects\pythonProject15\gf.py", line 178, in
result.plot_nodal_stress(0, comp='x')
File "E:\python3.10\lib\site-packages\ansys\mapdl\reader\rst.py", line 3433, in plot_nodal_stress
return self._plot_nodal_result(
File "E:\python3.10\lib\site-packages\ansys\mapdl\reader\rst.py", line 4894, in _plot_nodal_result
_, result = self._nodal_result(rnum, result_type)
File "E:\python3.10\lib\site-packages\ansys\mapdl\reader\rst.py", line 3707, in _nodal_result
raise ValueError(
ValueError: Result Nodal stresses (ENS) is not available in this result file.

Process finished with exit code 1

### 💻 Which operating system are you using?

Windows

### 📀 Which ANSYS version are you using?

2021 R2

### 🐍 Which Python version are you using?

3.10

### 📦 Installed packages

```shell
Pyansys

IDE : Pycharm
```

Start by reproducing the failure through result.plot_nodal_stress(0) or mapdl.post_processing.nodal_eqv_stress(), then inspect rst.py at plot_nodal_stress, _plot_nodal_result, and _nodal_result where the traceback reports the failure. Done means establishing why ENS is unavailable in this result file and documenting or correcting the supported behavior.

Written by the indexing model from the issue text.