[DOC] Update docker tag in documentation

[timothycarambat]

Description of changes

Summarize the changes made by this PR. The documentation for starting a container says to use chroma-core/chroma, which does not exist on the docker hub - it is called chromadb/chroma on the Docker Hub.

In order to pull and start a container the tag needs to be corrected.

Test plan

How are these changes tested?

• Correct command pulls docker image on fresh OS

Documentation Changes

• [x] Are all docstrings for user-facing APIs updated if required? Do we need to make documentation changes in the docs repository?