[gazelle] docs issues

[jab]

🐞 Errors in Gazelle docs

Description

The first code snippet in the Adding Gazelle to Your Project docs has errors.

1. It looks like python = use_extension("@rules_python//python/extensions:python.bzl", "python") needs to be added to avoid ERROR: /.../MODULE.bazel:12:10: name 'python' is not defined

2. The references to "python3_9" and "python3_9_toolchains" in the use_repo and register_toolchains calls are causing errors like ERROR: /.../rules_python_gazelle_plugin~/modules_mapping/BUILD.bazel:3:10: While resolving toolchains for target @@rules_python_gazelle_plugin~//modules_mapping:generator (f0f11f9): invalid registered toolchain '@python3_9_toolchains//:all': No repository visible as '@python3_9_toolchains' from main repository.

   I tried adding an underscore before the "3_9" as per this docstring ("A toolchain's repository name uses the format python_{major}_{minor}, e.g. python_3_10") but that didn't help. I commented all those references out and instead added python.toolchain(python_version="3.9", is_default=True), and seem to have gotten past this error, but I'm not sure if that has the exact same effect as the code that the docs intend you to add.

   While in there, would be good to update to a newer version of Python, as 3.9 is several releases old (3.12 is latest stable).

🌍 Your Environment

Operating System:

reproduced on macOS and Linux

Output of bazel version:

reproduced on various versions of Bazel 7

Rules_python version:

0.33.1