minor: remove python docs, now they're in another project

[kmitchener]

Which issue does this PR close?

Closes #2866

Rationale for this change

What changes are included in this PR?

Are there any user-facing changes?

[kmitchener]

@andygrove PTAL

[andygrove]

LGTM. Thanks @kmitchener. Once we have published the Python docs we should update here with a link to them.

[alamb]

Thanks @kmitchener -- can you remind me where the docs are now?

[kmitchener]

hey @alamb, sure, they've been moved to the arrow-datafusion-python project, in this PR apache/datafusion-python#23

[ursabot]

Benchmark runs are scheduled for baseline = 9e0bc50 and contender = b1765f7. b1765f7 is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ec2-t3-xlarge-us-east-2] ec2-t3-xlarge-us-east-2
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on test-mac-arm] test-mac-arm
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ursa-i9-9960x] ursa-i9-9960x
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ursa-thinkcentre-m75q] ursa-thinkcentre-m75q
Buildkite builds:
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