removed OPENBLAS_NUM_THREADS default from Malt.jl, fixes #233

[ajinkya-k]

See discussion in #233

[ajinkya-k]

@MichaelHatherly this should be enough to fix #233 right?

[MichaelHatherly]

this should be enough to fix #233 right?

Thanks @ajinkya-k, so the most important part of #233 in my mind is:

We can change the behaviour if it can be confirmed that it won't result in confusing errors for users.

It's better if users' notebooks don't fail, but may need to set the number of threads to something more than 1 if they need to increase performance, rather than failing for potentially hard to debug reasons and those users being required to add this env var to every single one of their notebooks to avoid errors.

If it can be confirmed that changing this setting doesn't introduce hard to debug errors for any users then we can. Is that something you have already done and can confirm?