Adds notice that --distributed is only available in beta. Fixes typo.

[Tomaz-Vieira]

A user was confused that ilastik would not recognize the --distributed flag, which is still only available on the beta version. This patch adds documentation to reflect that.

Also fixes a typo in the heading.

[k-dominik]

the feature is not available in any binary, currently - do you think it makes sense, given that we even in the docs recommend to install mpi4py via pip to make sure it's build correctly for the respective hpc cluster?

This would imply that we provide information on how to create such an installation with mamba/conda...

[Tomaz-Vieira]

Hmmm I'm not sure if I follow. Are you suggesting that we shouldn't advertise the feature since we don't provide an installation package for it?

[k-dominik]

Hmmm I'm not sure if I follow. Are you suggesting that we shouldn't advertise the feature since we don't provide an installation package for it?

I suggest we have instructions on there, how to create the environment with mamba/conda + pip, and be clear that it is in fact not enough to use some ilastik binary, no matter what version.

[k-dominik]

Hey @Tomaz-Vieira, this probably fell under the radar, but I think it would be very useful to document, how a user might set up an environment with mpi for their own cluster.