Update documentation

[joshcornejo]

https://github.com/hyperledger-labs/microfab/blob/main/docs/Tutorial.md

has instructions that no longer work

curl -sSL https://github.com/hyperledger-labs/microfab/releases/download/v0.0.18/microfab-linux-amd64 -o microfab

(/releases no longer exists ... not sure how to replace it?)

[jt-nti]

It looks like there's a v0.0.19 release which still has that file...

https://github.com/hyperledger-labs/microfab/releases/tag/v0.0.19