Docs: Fix regtest doc

[MonkeyCanCode]

1. Change outdated docker command to make client-regenerate
2. Remove reference for python3.9 as that is removed from Python client: remove Python 3.9 support #2795

[singhpk234]

LGTM Thanks @MonkeyCanCode !
can you please double confirm running the regtests that they work post this

[MonkeyCanCode]

Will do. I haven't do for this one as it was only doc change.

LGTM Thanks @MonkeyCanCode !
can you please double confirm running the regtests that they work post this

[MonkeyCanCode]

Will do. I haven't do for this one as it was only doc change.

LGTM Thanks @MonkeyCanCode !
can you please double confirm running the regtests that they work post this

hi @singhpk234, so if u tried to run the test locally (either with/without docker), it will always failed if u don't have the latest image built locally. This is because the docker file is now pointing to latest from dockerhub (version 1.2.0) but there is one breaking change on their build and it got fixed by @flyrain last week via https://github.com/apache/polaris/pull/2854/files (in this one, POST /v1/{prefix}/transactions/commit got print twice from catalog config). However, if u run the change with the local image (latest main), you will be able to get completed build:

regtest-1 exited with code 0

This has nothing to do with the changes in this PR. let me know if you have any concern before the merge.
cc. @flyrain

Thanks,
Yong

[singhpk234]

LGTM, thanks for checking and the code change @MonkeyCanCode