Updated Some MarkDown Files According to the Latest Release Version 1.4.0 of MMDetection3D

[ly3106]

Motivation

Make it easy to read for myself. And update some MarkDown files that some instructions are not suit to the latest MMDetection3D.

Modification

Some shell instructions and some super links that are 404.

BC-breaking (Optional)

Yes the modifications on instructions will break the back-compatibility of the downstream repos。 However, the breaking is not caused by these changes, rather, it stems from changes in the source codes.

Checklist

Yes