ARROW-17939: [Docs][Python] Update python dev page after PyArrow C++ tests change

[AlenkaF]

No description provided.

[github-actions]

https://issues.apache.org/jira/browse/ARROW-17939

[github-actions]

⚠️ Ticket has not been started in JIRA, please click 'Start Progress'.

[AlenkaF]

cc @pitrou @jorisvandenbossche: updating Python dev docs regarding PyArrow tests, if you want to have a look?

[AlenkaF]

I will use your phrasing for the Website blog post also, if you do not mind @pitrou =)

[pitrou]

No problem :-)

[ursabot]

Benchmark runs are scheduled for baseline = dcb9c90 and contender = 1349d59. 1349d59 is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Finished ⬇️0.0% ⬆️0.0%] ec2-t3-xlarge-us-east-2
[Failed ⬇️0.0% ⬆️0.0%] test-mac-arm
[Failed ⬇️0.0% ⬆️0.0%] ursa-i9-9960x
[Finished ⬇️0.36% ⬆️0.04%] ursa-thinkcentre-m75q
Buildkite builds:
[Finished] 1349d59c ec2-t3-xlarge-us-east-2
[Failed] 1349d59c test-mac-arm
[Failed] 1349d59c ursa-i9-9960x
[Finished] 1349d59c ursa-thinkcentre-m75q
[Finished] dcb9c90a ec2-t3-xlarge-us-east-2
[Failed] dcb9c90a test-mac-arm
[Failed] dcb9c90a ursa-i9-9960x
[Finished] dcb9c90a ursa-thinkcentre-m75q
Supported benchmarks:
ec2-t3-xlarge-us-east-2: Supported benchmark langs: Python, R. Runs only benchmarks with cloud = True
test-mac-arm: Supported benchmark langs: C++, Python, R
ursa-i9-9960x: Supported benchmark langs: Python, R, JavaScript
ursa-thinkcentre-m75q: Supported benchmark langs: C++, Java