MINOR: [Documentation] Add installation of ninja-build to Python Development docs

[albertvillanova]

Rationale for this change

Otherwise, you get a CMake error:

CMake Error: CMake was unable to find a build program corresponding to "Ninja".  CMAKE_MAKE_PROGRAM is not set.  You probably need to select a different build tool.

[jorisvandenbossche]

Thanks! Given the instructions after that explicitly use ninja, it indeed seems best to include that (although not strictly required)

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 4 benchmarking runs that have been run so far on merge-commit cc3c868.

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 2 possible false positives for unstable benchmarks that are known to sometimes produce them.