[DOC] links to docker hub in README.md are deprecated

[thawn]

Report incorrect documentation

in README.md, the links to docker hub still point at the deprecated images.

Location of incorrect documentation Readme.md line 8

Describe the problems or issues found in the documentation

base should point to (rapidsai/base)

notebooks should point to (rapidsai/notebooks).

Steps taken to verify documentation is incorrect List any steps you have taken: clicked on the existing links and found the deprecation notice on docker hub.

Suggested fix for documentation Update the links