CortxMotrQuickStart.md - points to invalid branch about cortx

[johnbent]

Thanks Jeetandra! @752708 can you please fix this in the documentation?

Jeetandra, by the way, the CORTX team, following Seagate guidelines on inclusivity, have recently been cleaning up our usage of offensive language. As such, we are replacing all usages of the word 'master' with 'dev' or 'main'.

[madhavemuri]

This issue is resolved now, main branch is added to cortx-motr repo.

[mukul-seagate11]

This issue is resolved now, main branch is added to cortx-motr repo.

Thanks for taking the action to resolve

[huanghua78]

This is fixed.