minor: doc fixes: fix link to datafusion-python project and add link to slides for rece…

[kmitchener]

…nt talk

Which issue does this PR close?

Closes #.

Rationale for this change

What changes are included in this PR?

Are there any user-facing changes?

[kmitchener]

@andygrove PTAL

[codecov-commenter]

Codecov Report

Merging #3118 (3dea765) into master (d527ca7) will decrease coverage by 0.00%.
The diff coverage is n/a.

❗ Current head 3dea765 differs from pull request most recent head e26983e. Consider uploading reports for the commit e26983e to get more accurate results

@@            Coverage Diff             @@
##           master    #3118      +/-   ##
==========================================
- Coverage   85.93%   85.92%   -0.01%     
==========================================
  Files         290      290              
  Lines       52295    52295              
==========================================
- Hits        44940    44937       -3     
- Misses       7355     7358       +3     

Impacted Files	Coverage Δ
datafusion/expr/src/window_frame.rs	92.43% <0.00%> (-0.85%)	⬇️
datafusion/core/src/physical_plan/metrics/value.rs	86.93% <0.00%> (-0.51%)	⬇️
datafusion/expr/src/logical_plan/plan.rs	77.60% <0.00%> (-0.18%)	⬇️

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[alamb]

Thanks @kmitchener !

[ursabot]

Benchmark runs are scheduled for baseline = 50fd12a and contender = c525e6c. c525e6c 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