Update reference-docs-generator, remove splice-wallet-kernel reference

[coldice]

Running the API Reference doc generation script with npm run generate:all-reference-docs results in errors:

Running: bash /Users/ibosy/work/b9lab/projects/canton/repos/docs-staging/scripts/generate_daml_standard_library_json.sh --output-json /Users/ibosy/.cache/x2mdx/daml-standard-library/json/3.4.9/modules.json --sdk-version 3.4.9 --package-set base --sdk-source dpm
Running: npm pack --silent @daml/types@3.4.8
[daml-docs-json] Generating daml-prim JSON
[daml-docs-json] source=dpm sdk=3.4.9 lf_target=2.2 package=daml-prim files=26
[daml-docs-json] Generating daml-script JSON
[daml-docs-json] source=dpm sdk=3.4.9 lf_target=2.2 package=daml-script dar=/Users/ibosy/.dpm/cache/components/daml-script/3.4.9/daml-script-2.2.dar entrypoints=2
Traceback (most recent call last):
  File "/Users/ibosy/work/b9lab/projects/canton/repos/docs-staging/scripts/generate_wallet_gateway_openrpc_reference.py", line 467, in <module>
    sys.exit(main())
             ~~~~^^
  File "/Users/ibosy/work/b9lab/projects/canton/repos/docs-staging/scripts/generate_wallet_gateway_openrpc_reference.py", line 384, in main
    selected_versions = stable_release_versions(
        release_repo=release_repo,
    ...<3 lines>...
        include_versions=include_versions,
    )
  File "/Users/ibosy/work/b9lab/projects/canton/repos/docs-staging/scripts/generate_wallet_gateway_openrpc_reference.py", line 134, in stable_release_versions
    releases_raw = gh(
        ["release", "list", "-R", release_repo, "--json", "tagName", "--limit", "1000"],
        capture=True,
    )
  File "/Users/ibosy/work/b9lab/projects/canton/repos/docs-staging/scripts/generate_wallet_gateway_openrpc_reference.py", line 96, in gh
    return run(["gh", *args], capture=capture)
  File "/Users/ibosy/work/b9lab/projects/canton/repos/docs-staging/scripts/generate_wallet_gateway_openrpc_reference.py", line 87, in run
    completed = subprocess.run(args, **kwargs)
  File "/nix/store/snai5drx7gf6nz1n3nqdxajhjszsjmg4-python3-3.14.4-env/lib/python3.14/subprocess.py", line 578, in run
    raise CalledProcessError(retcode, process.args,
                             output=stdout, stderr=stderr)
subprocess.CalledProcessError: Command '['gh', 'release', 'list', '-R', 'hyperledger-labs/splice-wallet-kernel', '--json', 'tagName', '--limit', '1000']' returned non-zero exit status 4.

[..]

Parallel reference-doc run finished with failures: generate_wallet_gateway_openrpc_reference.py

[coldice]

Was actually caused by gh not being found or logged in