Updating documentation

[mattdark]

I was following the instructions here and got some errors when running the instruction for connecting to the Percona Server for MongoDB container.

$ docker run -it --link psmdb --rm percona/percona-server-mongodb:mongo mongo -h psmdb

The mongo tag was not found:

Unable to find image 'percona/percona-server-mongodb:mongo' locally
docker: Error response from daemon: manifest for percona/percona-server-mongodb:mongo not found: manifest unknown: manifest unknown.
See 'docker run --help'.

Replaced the percona/percona-server-mongodb:mongo with percona/percona-server-mongodb:6.0. Then, the mongo command was not found:

+ exec mongo -h psmdb
/entrypoint.sh: line 464: exec: mongo: not found

Checked the MongoDB documentation and learned that the mongo shell was replaced with mongosh in MongoDB 6.0. The correct instruction should be:

$ docker run -it --link psmdb --rm percona/percona-server-mongodb:6.0 mongosh mongodb://MONGODB_SERVER:PORT/DB_NAME

This outdated information in the documentation was also reported in the forum.

[nastena1606]

Thank you for the contribution! LGTM