tools: remove pony ORM from our docs

[dikshant]

Dikshant Adhikari (dikshant) commented:

Pony ORM seems to be abandoned. The tool has not been updated for a while and CockroachDB support seems to be broken since Jan of last year. We should remove this tool from the list of supported third-party tools in our docs.
See: ponyorm/pony#667

Jira Issue: DOC-6606