Develop windows install instructions update

[dmalpica]

As discussed here: #1706

[vincentpierre]

I am not sure the Warning is necessary given that it is not a ML-Agents issue. Maybe adding a link to a CUDA documentation page that discusses this issue would be good if the Warning stays.
I am not a fan of having

python

<python code>

Because the two are in different languages. I would prefer : Open Python in the Prompt by calling

python

and then type the following commands

<python code>

to test if everything was installed properly

[dmalpica]

@vincentpierre Thanks for the feedback. I looked around but couldn't find a solid source documenting the issues I experienced, so I took out the warning.

That said, I found a more recent post that might be helpful:
https://www.pugetsystems.com/labs/hpc/The-Best-Way-to-Install-TensorFlow-with-GPU-Support-on-Windows-10-Without-Installing-CUDA-1187/

I addressed the other issue differentiating the anaconda prompt command from the python commands.

I am not sure the Warning is necessary given that it is not a ML-Agents issue. Maybe adding a link to a CUDA documentation page that discusses this issue would be good if the Warning stays.
I am not a fan of having

python

<python code>

Because the two are in different languages. I would prefer : Open Python in the Prompt by calling

python

and then type the following commands

<python code>

to test if everything was installed properly