Plotting errors during doc building

[germa89]

I am opening this issue for the record, and to go back to this in the future.

Disabling show_area_numbering in mapdl.vplot (See #2319), because I was getting the following error:

Extension error:
Here is a summary of the problems encountered when running the examples

Unexpected failing examples:
/home/runner/work/pymapdl/pymapdl/examples/00-mapdl-examples/pressure_vessel.py failed leaving traceback:
Traceback (most recent call last):
  File "/home/runner/work/pymapdl/pymapdl/examples/00-mapdl-examples/pressure_vessel.py", line 56, in <module>
    mapdl.vplot(color="grey", background="w", show_area_numbering=True, cpos="zy")
  File "/opt/hostedtoolcache/Python/3.10.13/x64/lib/python3.10/site-packages/ansys/mapdl/core/mapdl.py", line 1729, in vplot
    pl = self.aplot(
  File "/opt/hostedtoolcache/Python/3.10.13/x64/lib/python3.10/site-packages/ansys/mapdl/core/mapdl.py", line 1985, in aplot
    return general_plotter(meshes, [], labels, **kwargs)
  File "/opt/hostedtoolcache/Python/3.10.13/x64/lib/python3.10/site-packages/ansys/mapdl/core/plotting.py", line 835, in general_plotter
    pl = _general_plotter(
  File "/opt/hostedtoolcache/Python/3.10.13/x64/lib/python3.10/site-packages/ansys/mapdl/core/plotting.py", line 475, in _general_plotter
    labels = np.array(label["labels"])[idx - 1].tolist()
IndexError: index 8 is out of bounds for axis 0 with size 7

Additionally, I had to disable color, and cpos because I was getting:

Warning:  Reference not found for 'pyvista_docs' at line 4 column 90

generating gallery for examples/gallery_examples/01-geometry... [ 80%] 03-volumes.py
generating gallery for examples/gallery_examples/01-geometry... [100%] 04-primitives.py
2023-09-11 15:20:46.279 ( 671.050s) [        4CACDB80]vtkXOpenGLRenderWindow.:464    ERR| vtkXOpenGLRenderWindow (0x56128ff9d880): bad X server connection. DISPLAY=:99. Aborting.

Aborted (core dumped)
make: *** [Makefile:21: html] Error 134

https://github.com/ansys/pymapdl/pull/2319/files#diff-080fae7729900069f2c2a0d470479b279ccdd9bcf3c123d1d59c3dc344063fd8L56